"Three-and-a-Half Glasses of Milk Out of Five" Chocolate Ganache Cake

2 cups all-purpose flour
1 cup unsweetened cocoa
1 1/2 tsp baking soda
1 1/2 cups buttermilk
2 tsp vanilla extract
1 3/4 cups sugar
3/4 cup butter softened
3 large eggs
Bittersweet Chocolate Ganache:
5 ounces unsweetened chocolate chopped (I tend to not use unsweetened cocoa, I use either bittersweet chocolate chips, or a combination of semi-sweet and bittersweet)
¼ cup 1/2 stick chilled butter, cut into 1/2-inch cubes
1 teaspoon vanilla extract
¾ cup heavy whipping cream
¾ cup sugar

Preheat the oven to 350F.
Grease two 9-inch round cake pans with nonstick cooking spray or butter wrapper.
Mix together flour, cocoa and baking soda; in separate 2 cup measuring cup, mix together buttermilk and vanilla.
In a large bowl, cream butter and sugar together, gradually increasing speed from low to high. Beat on high for 3 minutes or until creamy, occasionally scraping bowl with spatula. Reduce speed to low; add eggs one at a time, beating well after each addition.
Beat in flour mixture alternately with buttermilk, beginning and ending with the flour, scraping bowl occasionally.
Pour batter into prepared pans. Bake until toothpick inserted in center of cake comes out clean (for me, no longer than 30 minutes). Cool in pans on wire racks for 10 minutes, then invert cakes onto wire cooling racks to cool completely before frosting.
Place chopped chocolate, butter, and vanilla in medium bowl.
Bring cream and sugar to boil in medium saucepan, stirring to dissolve sugar.
Carefully pour hot cream mixture into bowl with chocolate. Let stand 1 minute. Whisk until melted and smooth. Chill ganache until thickened and spreadable, about 1 hour. Frost cake.