Preheat oven to 350°. In a large bowl, cream butter and brown sugar until light and fluffy, 5-7 minutes. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine flour, cocoa, baking soda and salt; add to creamed mixture alternately with coffee and sour cream, beating well after each addition.
Pour into three greased and floured 9-in. round baking pans. Bake until a toothpick inserted in the center comes out clean, 30-35 minutes. Cool 10 minutes before removing from pans to wire racks to cool completely.
In a large bowl, beat cream cheese and butter until fluffy. Beat in the chocolate, coffee and vanilla until blended. Gradually beat in confectioners' sugar. Spread between layers and over top and sides of cake. Cover and refrigerate until serving.