1. Heat oven to 350°F. Grease and flour 13x9x2-inch baking pan.
2. Stir together flour, granulated sugar, brown sugar, baking soda, cinnamon and salt in large bowl. Stir together eggs, oil and vanilla in small bowl; stir into dry ingredients, blending well. Stir in carrot, peanut butter chips and 1/2 cup walnuts. Pour batter into prepared pan.
3. Bake 35 to 40 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack. Frost with CREAM CHEESE FROSTING. Garnish with walnuts, if desired. 12 to 15 servings.
CREAM CHEESE FROSTING: Beat 1 package (3 oz.) softened cream cheese and 1/4 cup (1/2 stick) softened butter or margarine in small bowl until well blended. Gradually add 2 cups powdered sugar and 1 teaspoon vanilla extract, beating to spreading consistency.
VARIATION: Substitute 1 cup raisins for the chopped walnuts.
PEANUT BUTTER CHIP CARROT CUPCAKES: Line muffin cups (2-1/2 inches in diameter) with paper bake cups. Fill muffin cups 3/4 full with batter. Bake 25 to 30 minutes or until wooden pick inserted in center comes out clean.