Preheat oven to 350 degrees F. Line 18-24 muffin cups with cupcake liners.
Cupcakes: In a medium bowl, combine flour, Clabber Girl Baking Powder, Clabber Girl Baking Soda, salt and lavender; set aside. In a separate bowl, combine the vanilla extract and buttermilk. In a large bowl, cream the butter and sugar until fluffy. Add the eggs one at a time and beat until combined. With the mixer on low speed, add the flour mixture in 2 equal portions, alternating with the buttermilk mixture, starting and ending with the flour mixture. Mix after each addition until just combined.
Divide the batter evenly among the cupcake liners, filling each about 2/3 full. Bake the cupcakes for 20 to 30 minutes. To test for doneness, insert a toothpick in the middle of a few cupcakes and remove ensuring the toothpick is free of batter when removed. Remove the cupcakes from the oven and immediately place pans on a wire cake rack and cool for 5 minutes before turning cupcakes out onto the rack to cool.
Frosting: Beat butter until smooth and fluffy. Add half of the confectioners' sugar (1/2 c. at a time) and beat until incorporated. Add 2 tbsp. of the heavy cream, vanilla extract and lavender then mix well on medium speed. If mixture is too stiff, add more milk until the mixtures is creamy.