01 - Preheat oven to 350°F. Grease and line an 8-inch square baking pan.
02 - In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt until well blended.
03 - Add buttermilk, oil, egg, and vanilla to the dry mixture. Mix until smooth. Pour in hot water and mix again until combined.
04 - Pour batter into prepared pan. Bake for 25-30 minutes until a toothpick inserted in center comes out clean. Cool completely.
05 - While cake cools, whip heavy cream with powdered sugar and vanilla (and cream cheese if using) until medium-stiff peaks form. Refrigerate until ready to use.
06 - Break cooled cake into small pieces and crumble into fine texture with hands or fork.
07 - Fill clean flower pots or dessert cups in layers: crumbled cake, cream filling, more cake crumbs, then generous chocolate cookie crumb topping.
08 - Arrange edible flowers, mint leaves, and herb sprigs on top of cookie crumb soil to resemble a growing garden.
09 - Refrigerate assembled desserts for at least 30 minutes to set flavors and texture before serving.