Microwave butter and chocolate in large microwaveable bowl on Medium 3 minutes or until butter is melted. Stir until chocolate is completely melted.
Add eggs; beat until well blended. Srir in sugar, flour and walnuts. Spread into greased 13x9-inch baking pan.
Bake 30 minutes or until a toothpick inserted in the center comes out with the fudgy crumbs. (Do not overbake). Cut into 24 squares to serve.
PHILADELPHIA SWIRL BROWNIES: Prepare brownie batter and spread in baking pan as directed; set aside. Mix 1 package (250g) softened Philadelphia cream cheese and 1/4 cup sugar until well blended. Stir in 2 tablespoons Pure red Raspberry jam and 1 egg. Drop teaspoonfuls of the cream cheese mixture over brownie batter in pan; cut through batters several times with knife for marble effect. Bake as directed. Cool completely. Cut into squares as directed. Store in tightly covered containers in refrigerator.
ROCKY ROAD BROWNIES: Prepare as directed, topping the brownies wirh miniature marshmallows and Baker's semisweet chocolate chips for the last 5 minutes of the baking time.
PEANUT BUTTER SWIRL BROWNIES: Prepare as directed. Immediately after removing brownies from oven, drop 12 tablespoons of Peanut Butter over hot brownies; sprinkle with 2 squares chopped Baker's semisweet chocolate. Let stand until melted, then swirl lightly with knife for marble effect. Cool completely before cutting to serve.
EASY FROSTING: Prepare brownies as directed; cool completely. Prepare 1 package (113g) instant pudding, chocolate, vanilla or butterscotch flavor as directed on package; reducing the milk to 1 1/2 cups. Gently stir in 1 cup thawed Cool Whip Topping . Spread over brownies. REfrigerate until set.