Roll about 1/2 teaspoon modeling chocolate into a 1/2-inch ball; set aside. This is the bunny's nose.
Roll 1/2 teaspoon modeling chocolate into a 3/4-inch V shape; set aside. This is the bunny's mouth.
To make the hair, roll out 2 tablespoons modeling chocolate to a 3-by-5-inch rectangle, 3/16 inch thick. With a paring knife, trim to a 4 1/2-inch-tall-by-2-inch-wide triangle. Trim off top 2 1/4 inches of triangle; set aside. Slice vertically 1/2 inch down from top, into 1/8-inch strips; set aside.
To make the paws, shape 2 ounces or 1/4 cup modeling chocolate into a 1 1/2-inch cylinder. Divide in half, and mold into teardrop shapes. Press larger side with thumb to flatten. Fold over 1/4-inch of larger side. Press thumb underneath folded portion to indent. Score top side of fold four times with paring knife; set aside.
To make the bow tie, roll out 2 tablespoons modeling chocolate to 1/8 inch thick. Cut into a strip about 8 by 1 1/4 inches. Cut a second strip about 2 inches long and 1/2 inch wide. Bend the ends of the longer strip so that they meet in the center. Shape smaller strip around to form the knot; set aside.
To make the tail, shape about 1 tablespoon modeling chocolate into a 1 1/2-inch round ball. Flatten slightly with thumb; set aside. "Spackle" with a pastry brush that has been dipped in tempered bittersweet chocolate.
To temper bittersweet chocolate, place 1 1/4 pounds (about 4 cups) bittersweet chocolate in a medium stainless-steel bowl set over a saucepan of simmering water. Stirring frequently, melt chocolate to 118 degrees.to 120 degrees.
Remove bowl of chocolate from heat, and add remaining 1 3/4 pounds (about 5 1/2 cups) bittersweet chocolate, stirring constantly to cool chocolate to 80 degrees.to 82 degrees. Return bowl of chocolate over simmering water for about 1 minute. Remove from heat; stir constantly to melt chocolate to 88 degrees.to 90 degrees. If chocolate is lumpy, return bowl over simmering water for 3 to 5 seconds at time. Remove from heat, and continue stirring until lumps disappear. Check for temper by dipping the tip of a small offset spatula into chocolate. Set spatula aside to allow chocolate to dry. Chocolate is tempered if it dries shiny and hard. Set bowl of tempered chocolate aside on a heating pad with extra cushion to keep from overheating while tempering white chocolate.
To temper white chocolate, place 10 ounces (about 2 cups) white chocolate in a medium stainless-steel bowl set over a saucepan of simmering water. Stirring frequently, melt chocolate to 104 degrees.to 106 degrees.
Remove bowl of chocolate from heat, add remaining 8 ounces (about 1 1/2 cups) white chocolate, stirring constantly to cool chocolate to 78 degrees.to 80 degrees. Return bowl of chocolate over simmering water for about 30 seconds. Remove from heat; stir chocolate to melt chocolate to 82 degrees.to 84 degrees. If chocolate is lumpy, return bowl over simmering water for 3 seconds at a time. Remove from heat, and continue stirring until lumps disappear. Check for temper by dipping the tip of a second small offset spatula into chocolate. Set spatula aside to allow chocolate to dry.
Line a baking pan with parchment paper; set aside. Gather 4 ramekins; set aside. Completely fill two 5 5/8-inch egg molds to the rim (available at baking supply stores) with tempered bittersweet chocolate.
Gently drop mold on work surface to expel air bubbles. Set filled mold aside on a flat surface until molten chocolate nearest the mold begins to set and form a shell, 3 to 5 minutes.
Invert filled mold over tempered chocolate bowl to pour out excess chocolate. The inside of the mold will be evenly covered with a thin layer of chocolate that will form the eggshell. Using an offset spatula, scrape chocolate off of flat surface of mold.
Place the mold, dome-side up, with each corner resting over a ramekin set on the prepared baking pan to dry, 3 to 5 minutes. This "rack" allows air to circulate in molds and chocolate to dry.
Remove mold from ramekins. Using an offset spatula, scrape away any excess chocolate around edge of egg so that chocolate is flush with the top of mold.
Set mold aside, dome-side down, to continue drying for about 20 minutes. Before unmolding, chill for 5 to 10 minutes in the refrigerator. Carefully remove chocolate eggshells from mold.
Place a baking pan upside down over a pot of simmering water. Place both 5 5/8-inch eggs dome-side up on warm sheet pan until edges barely begin to melt, about 5 seconds. Adhere both halves to form a large egg. Place on an egg crate (to prevent rolling) to dry, 3 to 5 minutes.
Repeat Steps 5 and 6 with two 3 1/2-inch egg molds for the feet and two 3 5/8-inch dome molds for the head.
Repeat Steps 5 and 6 using the tempered white chocolate to fill two 1 1/2-inch egg molds.
To make the ears, draw two 6-inch-long ears onto parchment paper. Cut out ears, and place on a level surface. Drizzle about 3 tablespoons tempered chocolate over each ear to cover. With a small spatula, smooth to a 1/8-inch thickness. Transfer ears to a clean surface. Fold over top one-third of one ear, and turn on side. Allow ears to dry for about 5 minutes before peeling away parchment paper.
To make the eyes, fill one small cornet (small paper pastry cone) with 1 to 2 tablespoons tempered white chocolate and one small cornet with the same amount tempered bittersweet chocolate. Using scissors, cut off 1/8 inch of tips. Place a piece of parchment on a level surface. Beginning with the white chocolate, pipe 1 1/4-inch ovals onto parchment paper. With the bittersweet chocolate, immediately pipe 3/4-inch circles inside center of ovals. With the white chocolate, immediately pipe 3/8-inch dots right on center of dark-chocolate circles. Set chocolate-filled cornets aside in a warm spot to be used again for assembly. Allow eyes to dry for about 5 minutes before peeling away from parchment paper.
To make the feet, place a piece of parchment paper onto a level surface. Drizzle 3 tablespoons of tempered bittersweet chocolate onto center of parchment paper; smooth with a small offset spatula to a large oval shape, 1/8 inch thick. Immediately place both 3 1/2-inch chocolate eggs hollow-side down on pooled chocolate. After 1 minute, using a paring knife, trace outline of eggs. Allow to dry 3 to 5 minutes before peeling eggs away from parchment paper.
Place a pan upside down over simmering water. Place both 5 5/8-inch eggs hollow-side down on warm sheet pan until eggs barely begin to melt, about 5 seconds. Adhere both halves to form a large egg. Place on an egg crate (to prevent rolling) to dry, 3 to 5 minutes. Repeat this process with the 3 5/8-inch chocolate domes to make a ball.
To assemble the bunny, place a piece of parchment paper on a level surface. Pool 2 to 3 teaspoons of tempered bittersweet chocolate onto center of parchment paper. Immediately heat the larger end of chocolate egg on the pan over simmering water until it just begins to melt and creates a level surface, about 5 seconds. Immediately place egg, melted-side down, into pooled chocolate so that the egg stands level. This is the bunny's body.
Place seam of chocolate ball onto the heated half-sheet pan to melt a dime-size hole, about 5 seconds. With reserved dark-chocolate cornet, pipe one layer of tempered chocolate around perimeter of hole. Invert onto top of body to attach. This is the bunny's head.
To attach the feet, use a paring knife, and score a 1/2-inch pound sign (#) onto the center of domed side of feet. Score the body with two 1/2-inch pound signs (#) about 2 inches apart, 1 1/2 inches up from the bottom. Dip the scored portion of feet into tempered bittersweet chocolate, and adhere to scored portion of body, smallest side up.
Touch 1 1/2-inch white-chocolate eggs to the heated half-sheet pan until they just begin to melt, 3 to 5 seconds. Attach to head about 1/8 inch apart, small ends out. These are the bunny's cheeks.
Attach eyes with tempered bittersweet chocolate.
Attach ears in back center of head, spacing them about 1/2 inch apart, with tempered bittersweet chocolate.
Dip pastry brush into tempered bittersweet chocolate, and "spackle" front side of ears.
Attach reserved modeling chocolate pieces with tempered bittersweet chocolate.