In heavy saucepan, melt 1 cup chocolate chips with butter, stirring constantly. Beat egg with sugar, brown sugar and vanilla until creamed. Mix in melted chocolate. Stir flour with baking soda, baking powder and salt. Combine milk with lemon juice stirring until thick. Add dry ingredients to chocolate mixture alternately with milk. Stir in nuts and remaining cup chocolate chips. Chill dough. Drop by teaspoon onto ungreased baking sheet. Bake at 350 F for 8-10 minutes. Cool on rack.