1. Cupcakes: Preheat oven to 350 degrees with rack in center. Line two standard muffin tins with 18 paper liners. In a medium bowl, whisk together flours, baking powder, baking soda, and salt.

2. In the bowl of an electric mixer fitted with the paddle attachment, beat together butter and sugar on medium speed until fluffy. Beat in vanilla seeds. Add eggs and yolks, one at a time, beating until each is fully incorporated before adding the next. Reduce speed to low; gradually add flour mixture in three batches, alternating with buttermilk, beginning and ending with flour mixture and beating until combined after each addition.

3. Using an ice cream scoop or large spoon, divide batter evenly among muffin cups, filling each two-thirds full. Bake, rotating pans halfway through, until cupcakes spring back when lightly pressed and a tester inserted into centers comes out clean, about 16 minutes. Transfer to a wire rack and let cool completely.

4. Buttercream: Combine egg whites, sugar, and salt in the heatproof bowl of a mixer set over (not in) a pot of simmering water. Whisk constantly until sugar is dissolved, and mixture is warm to the touch and feels completely smooth when rubbed between fingertips.

5. Transfer bowl to mixer fitted with the whisk attachment. Starting on low speed and gradually increasing to medium-high, whisk until stiff (but not dry) peaks form. Continue whisking until meringue is fluffy and glossy, and completely cool (test by touching the bottom of the bowl), 6 to 8 minutes.

6. Reduce speed to medium-low and add butter a few tablespoons at a time, whisking well after each addition. Whisk in vanilla. Switch to paddle attachment and beat on low speed until all air bubbles are eliminated, about 2 minutes. Scrape down sides of bowl with a flexible spatula; continue beating until frosting is completely smooth. Keep buttercream at room temperature if using same day. If not, transfer to an airtight container and refrigerate up to 3 days or freeze up to 1 month. Before using, bring to room temperature and beat with paddle attachment on low speed until smooth again, about 5 minutes.

7. Reserve 1/2 cup buttercream. Tint remaining buttercream green, adding food color a drop at a time until desired color is reached. If necessary, use reserved buttercream to lighten color.

8. Transfer buttercream to a pastry bag fitted with a small multi-opening tip (such as Wilton #233). Starting at the center and moving outward, pipe grass on top of cupcake: With tip on surface of cupcake, squeeze bag, then release while quickly pulling up to form 1/2-inch-long blades. Pipe some slightly longer for a realistic look.

9. Marzipan Ladybugs: Tint marzipan red, adding a small amount of food color and kneading until thoroughly incorporated, until you reach desired color.

10. Pinch off eighteen 1 teaspoon-sized pieces of marzipan and shape into ovals for ladybug bodies. Using the back of a paring knife, score a line lengthwise along surface of each body to form wings. Place a chocolate chip at one end of each body, point-side out, to form heads. Insert chocolate pearls into wings to form spots. Place a ladybug on top of each frosted cupcake.