We used six unglazed, untreated terra-cotta flowerpots (each with a six-ounce capacity, about 3 inches tall and 3 1/2 inches across the top). Thoroughly wash the new pots in hot water before using.
- 1/3 cup vegetable oil, plus more for pots
- 3/4 cup unsweetened cocoa powder, plus more for dusting
- 1 1/2 cups all-purpose flour
- 1 1/2 cups sugar
- 1 1/2 teaspoons baking soda
- 3/4 teaspoon baking powder
- 3/4 teaspoon salt
- 1 large egg, plus 1 large egg yolk
- 3/4 cup buttermilk
- 3/4 teaspoon pure vanilla extract
- Quick Chocolate Frosting
- 1/2 cup crushed chocolate wafer cookies (about 10), for garnish
- Multicolored pebble-shaped chocolate candies, for garnish
- Mint sprigs, for garnish
Preheat oven to 350 degrees. Brush inside of each flowerpot with oil, and line bottom with parchment paper round. Brush parchment with oil, and lightly dust with cocoa.
Sift cocoa, flour, sugar, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with the paddle attachment. Add egg and yolk, 3/4 cup warm water, buttermilk, oil, and vanilla; mix on low speed until smooth, about 1 minute.
Divide batter among prepared pots, filling each about two-thirds full. Transfer to a rimmed baking sheet. Bake, rotating sheet about halfway through, until a cake tester inserted into centers comes out clean, 45 to 50 minutes. Let cakes cool completely in the flowerpots on a wire rack.
Frost cakes with an offset spatula; sprinkle with crushed cookies. Top with candies; "plant" 1 mint sprig in each cake.