Preheat oven to 350°F
Spray 3 9-inch round baking pans with pam, line bottoms with parchment paper, grease again and set aside.
In small bowl combine cocoa and boiling water with a whisk until smooth. Cool.
In medium bowl stir together flour, baking soda and salt.
In a mixer, beat butter and sugar until fluffy.
Add eggs, one at a time and vanilla.
Slowly add the cocoa mix.
Add 1/3 of the flour mix, then the milk. Then 1/3 of flour and the sour cream. Then, add the past of the flour.
Mix well and divide into the pans.
Bake 20-22 mins until the toothpick comes out clean.
Cool and pop out of pans. Remove parchment,