Heat Oven to 325 degrees f.
Melt butter and chocolate in a 3 quart heavy saucepan over
low heat, stirring constantly. Cool. Add sugar and eggs,
1 at a time, and mix until blended after each addition. Blend
in milk and vanilla. Stir in combined flour and salt, mixing
just until blended. Spoon into greased and floured 9X3 spring-form
Bake 25 minutes.
Beat cream cheese, sugar and vanilla at medium speed with
electric mixer until well blended. Blend in sour cream, then
pour over brownie bottom. (Filling will come almost to the
top of pan}. Bake 55 to 60 minutes, or until center is almost
set. Run knife or metal spatula around rim of pan, to loosen
cake. Cool before removing rim of pan. Refrigerate for 4
hours, or overnight. Let stand at room temperature before
Drizzle with assorted ice cream toppings, if desired.