A favorite flower of the Victorians, the sweet pea was thought to represent delicate pleasures. Exquisite buttercream renditions of the flower grace this layer cake. A beaded icing "frame" gives them the look of treasured pressed blooms.
Tint 5 1/4 cups frosting pale pink (for filling and base coat). With a small offset spatula, spread top of bottom cake layer with 1 1/4 cups pale-pink frosting; carefully slide the second cake layer back on top of the first layer.
With a serrated knife, trim cake to measure 8 by 11 inches. Gently brush away loose crumbs from top and sides of cake with a pastry brush. With the offset spatula, spread about 1 1/2 cups pale pink frosting over top and sides of cake to form a crumb coat. Refrigerate cake until frosting is firm, about 15 minutes.
With a large offset spatula, spread about 2 more cups pale-pink frosting over top and sides to form a second coat. Smooth top and remove excess frosting with the large offset spatula. Smooth sides with a bench scraper. Return cake to refrigerator, and chill until second coat is firm, about 15 minutes.
Tint 1 1/2 cups frosting each pale pink and dark pink (for flowers). Tint 3/4 cup each pale peach and peach (for more flowers). Tint 3/4 cup green (for leaves, stems, and calyxes). Set aside.
Using a toothpick or wooden skewer, mark a pattern on the frosting to serve as a guideline for piping stems.
Decorate cake: Pipe stems using green frosting and the #2 tip. Then, using pink frosting and the #103 petal tip, form two basic petals, side by side: Hold the bag at a 45 degree angle to the cake, with the tip's wide end down and narrow end pointed away and slightly to the left. Move the tip forward 1/8 inch and back again while you pivot the narrow end to the right. Pipe two smaller petals overlapping each other on top of the first two. Switch to a lighter-color frosting; hold bag at 90 degrees to the flower with wide end facing forward, and pipe a center, pulling down slightly. Switch to green frosting and the #352 leaf tip: Starting at the base of the bloom with the tip's pointed end facing up, pipe small leaves, pulling tip toward flower. For small blooms and buds, make fewer petals. Add curlicues with the #1 tip.
Refrigerate cake until ready to serve. Let stand at room temperature 20 minutes before serving. Slice into squares: To avoid crumbs on surface, make each cut with one downward motion, pulling knife back toward you (not upward) and wiping knife clean after each cut.
Cake can be refrigerated for up to four hours.