Ghirardelli Mississippi Mud Bars

Here's a sweet snack from the kitchen of Cheryl Hoefler, my co-worker. She found the recipe on the packaging of a Ghirardelli White Chocolate Baking Bar.

½ C. butter or margarine, softened
3/4 C. brown sugar, firmly packed
1 tsp. vanilla
1 large egg
1 C. all-purpose flour
½ tsp. baking powder
1/4 tsp. salt
1 bar (4 oz.) Ghirardelli Semi-Sweet Chocolate Baking Bar, chopped and divided
1 bar (4 oz.) Ghirardelli White Chocolate Baking Bar, chopped and divided
1 C. walnuts, chopped and divided

Preheat oven to 350 F.
In a large bowl, beat butter, sugar, egg and vanilla until light and fluffy at medium speed.
Mix in flour, baking soda and salt.
Stir in half of the semi-sweet and white chocolate and ½ C. of the walnuts.
Spread in greased foil-lined 9" square baking pan.
Bake 12-15 minutes or until toothpick inserted in center comes out almost clean.
Sprinkle with remaining semi-sweet and white chocolates.
Cover with foil. Let stand 5 minutes or until chocolates are melted.
Swirl chocolates with small knife to marbleize.
Sprinkle with remaining ½ C. walnuts.
Cool in pan until firm, then cut into bars.
Makes 1-12 servings.