1/2 c. unsalted butter
3 oz. unsweetened chocolate
3/4 c. granulated sugar
1/2 c. brown sugar
1/2 tsp. baking powder
1/2 tsp. baking soda
1 large egg
1 tsp. vanilla extract
1/2 c. flour
1/2 c. sour cream
6 oz. milk chocolate chips
6 oz. white chocolate chips

Preheat oven to 350°F. Use 2 insulated cookie sheets to protect bottoms of cookies.

Melt butter and chocolate chips together in a covered microwavable dish for 2 minutes. Remove mixture and stir with a whisk until smooth. Cool for approximately 5 minutes.

Using an electric mixer on medium speed, combine sugar, brown sugar, baking powder and baking soda for 20 seconds. Add egg and vanilla; beat on medium speed for 2 minutes or until fluffy and light in color. Scrape bowl with a spatula and add 3/4 cup flour; beat on low speed for 20 seconds, or just until blended. Scrape the bowl again and add sour cream. Scrape the bowl one more time and add remaining flour and all chocolate chips. Mix on low speed just until the flour is blended in.

Drop dough by rounded tablespoonfuls onto baking sheets and bake for 13 to 15 minutes. Reversing baking sheets and switching them top to bottom half-way though baking time. Do not over bake. Remove the pans from oven and set on wire cooling rack.

Makes 4 dozen 3-inch cookies.