This classic chocolate layer cake is one for the record books. The ideal ending (if you can wait that long!) to dinner.
Preheat oven to 350°F (180°C). Grease and flour two 9-inch (1.5 L) round baking pans.
Beat butter with sugar, eggs and vanilla in a large bowl until fluffy. Combine flour with cocoa, baking powder, baking soda and salt; add alternately with the buttermilk to the butter mixture, beating until smooth. Divide batter between prepared pans.
*To sour milk: Use 4 1/2 tsp (22 mL) white vinegar plus milk to equal 1 1/2 cups (375 mL).
Bake for 30 to 35 minutes or until a wooden pick inserted in the centre comes out clean; cool in pans for 10 minutes. Remove cake from pans to a rack; cool completely.
Chocolate Fudge Frosting: Melt butter in a small saucepan set over low heat; add cocoa. Cook, stirring constantly, until smooth and slightly thickened. Remove from heat; pour into medium bowl. Cool until very thick (about 40 minutes). Add icing sugar alternately with milk and vanilla; beat until a spreadable consistency is achieved. Frost cooled cake.