Melt chocolate and 3 tbsps. butter over very low heat, stirring constantly. Cool.
Cream remaining butter with the cream cheese until softened. Gradually add 1/4 cup sugar, creaming until light and fluffy. Stir in one egg, 1 tablespoon flour, and 1/2 teaspoon vanilla until blended. Set aside.
Beat remaining eggs until fluffy and light in color.
Gradually add remaining 3/4 cup sugar, beating until thickened.
Fold in baking powder, salt, and remaining 1/2 cup flour.
Blend in cooled chocolate mixture. Stir in nuts, almond extract, and remaining 1 teaspoon vanilla. Measure 1 cup chocolate batter and set aside.
Spread remaining chocolate batter in a greased 8 or 9 inch square pan.
Pour cheese mixture over the top. Drop measured chocolate from tablespoon onto the cheese mixture; swirl the mixtures together with a spatula just to marble.
Bake at 350 degrees for 35 to 40 minutes. Cool. Cut into bars or squares.
Cover and store in refrigerator.