Ooey-Gooey Chocolatey Goodness Cake

CAKE:
1 box chocolate cake mix (devil's food or milk chocolate)
1 small box (4 1/2-serv. size) instant chocolate pudding mix (1/2 cup + 1 Tblsp.)
1 cup sour cream
1 cup oil
4 eggs, beaten
1/2 cup milk
1 tsp. vanilla
1-1/2 cups mini chocolate chips

Preheat oven to 350 F.

In large bowl, mix all ingredients (except chocolate chips).  Fold in chocolate chips.  Pour batter into two greased and floured or paper-lined 9" round cake pans or one 13" x 9" baking pan.

Bake 30 to 45 minutes or until cooked through and set. Use your best judgment - checking with a knife or toothpick doesn't work well with this cake because it's filled with melted chocolate chips.

Cool COMPLETELY, frost with Chocolate Buttercream Frosting (recipe below), and decorate as desired.

FROSTING:
1 cup (2 sticks) unsalted butter, softened
3 1/2 cups powdered sugar
1/2 cup cocoa
1/2 tsp. salt
2 tsp. vanilla
4 Tblsp. heavy cream or milk

Cream butter on medium speed for 2 minutes.  Add sugar and cocoa; mix slowly just until combined.  Add vanilla, salt, and cream/milk; beat on medium speed for another 3 minutes.

For thicker consistency, add more sugar.  For thinner consistency, add more cream/milk one tablespoon at a time.