Preheat oven to 350F and oil an 8x8 brownie pan. In a blender, combine avocado, milk, sugar, agave, and vanilla extract. Blend 15-20 seconds, or until smooth.
In a medium mixing bowl, stir together dry ingredients (flour, cocoa powder, baking soda, salt).
Make flax egg by combining 1 tablespoon ground flax seed with 2 tablespoon water. Stir and let set for two minutes before using.
Pour avocado mixture into dry ingredients, stirring to combine. Add flax egg to brownie mixture, stirring until fully combined. Pour brownie batter into greased pan.
Bake for 25 minutes, or until a toothpick inserted in the center comes out clean. Let sit for 5 minutes before cutting and serving.
Strawberry Icing
Combine powdered sugar, vanilla, and thawed strawberries in a blender. Blend until smooth. If icing is too thin, add extra powdered sugar. If too thick, add a teaspoon of milk at a time.