Heat 1/4 cup milk with 2 tablespoons dried culinary lavender in a small saucepan.

Allow to cool and put the lavender in the fridge to steep for about four hours.

Preheat the oven to 350° Fahrenheit (177° Celsius).

Grease three 8-inch cake pans and coat with cocoa powder (this prevents the white lines that you would get on your cake from dusting the cake pans with flour).

In a large mixing bowl or stand mixer bowl, combine the sugar, flour, baking powder, salt, baking soda, and dark cocoa powder. Add the eggs one at a time and mix after each one.

Add the milk, vanilla, and vegetable oil and mix until incorporated.

Stir in the boiling water.

Divide the batter into the three cake pans. Use a silicone spatula to evenly spread out the batter in each pan, making sure to get into all the corners.

Bake 22-25 minutes or until a toothpick inserted in the center comes out clean. Let the cake layers cool in the pans for about 10 minutes, then remove them from the pans and transfer to wire baking racks to cool completely.

Beat the softened butter with an electric mixer. Carefully add 3 cups of powdered sugar and beat until uniform in color.

Get the lavender that we steeped with milk in the fridge earlier. Strain the lavender by pouring it into a sieve.

Add this lavender-infused milk, vanilla extract, and the remaining powdered sugar to the frosting. Beat until smooth and tint the frosting your desired shade of purple.

Spread the frosting on each of the three layers of cake and put them on top of each other.

Garnish the top with the blackberries and edible flowers.