Preheat the oven to 350°F (175°C).

Grease a 13x9x2-inch baking pan or two 8-inch square baking pans.

In a large bowl, stir together the cocoa and baking soda.

Add ⅓ cup melted butter and boiling water.

Stir until the mixture thickens.

Mix in the sugar, eggs, and remaining ⅓ cup melted butter until smooth.

Add the flour, vanilla extract, and salt, blending completely.

Fold in the chocolate chips.

Pour the batter into the prepared pan(s).

Bake for 35-40 minutes for a rectangular pan or 30-35 minutes for square pans, or until the brownies begin to pull away from the sides of the pan.

Let the brownies cool completely in the pan on a wire rack.

Frost with one-bowl buttercream frosting and cut into squares before serving.

Heat oven to 350°F.

Grease 8-inch square baking pan.

Beat butter and sugar in large bowl until light and fluffy.

Add egg and vanilla; beat well.

Stir together flour, graham cracker crumbs, baking powder and salt; add to butter mixture, beating until blended.

Press half of dough into prepared pan.

Arrange chocolate bars over dough, breaking as needed to fit.

Spread with marshmallow creme.

Scatter bits of remaining dough over marshmallow; carefully press to form a layer.

Bake 30 to 35 minutes or until lightly browned.

Cool completely in pan on wire rack.

Cut into bars.

Heat oven to 350°F.

Grease 9-inch square baking pan.

Stir together chocolate chips, marshmallows and nuts; set aside.

Place butter in large microwave-safe bowl.

Microwave at HIGH (100%) 1 to 1-1/2 minutes or until melted.

Add sugar, vanilla and eggs; beat with spoon until well blended.

Add flour, cocoa, baking powder and salt; stir until well blended.

Spread batter into prepared pan.

Bake 22 minutes.

Sprinkle chocolate chip mixture over top.

Continue baking 5 minutes or until marshmallows have softened and puffed slightly.

Cool completely in pan on wire rack.

Using wet knife, cut into squares.

Heat oven to 350°F.

Grease 13x9x2-inch baking pan.

Combine flour and brown sugar in large bowl.

Cut in butter until mixture resembles coarse crumbs.

Add egg; mix well. S

tir in 1-1/2 cups chocolate chips and nuts; set aside 1-1/2 cups mixture.

Press remaining crumb mixture onto bottom of prepared pan.

Bake 10 minutes.

Pour sweetened condensed milk evenly over hot crust; set aside 1/4 cup toffee bits.

Sprinkle remaining toffee bits over sweetened condensed milk.

Sprinkle reserved crumb mixture and remaining 1/2 cup chips over top.

Bake 25 to 30 minutes or until golden brown.

Top with reserved toffee bits.

Cool completely in pan on wire rack.

Cut into bars.

Heat oven to 350°F.

Grease 15-1/2×10-1/2×1-inch jelly-roll pan.

Stir together brown sugar, butter and granulated sugar in large bowl; beat in eggs and vanilla.

Add flour and salt, beating just until blended.

Set aside 2 tablespoons each milk chocolate chips and peanut butter chips.

Stir remaining chips in batter; spread batter in prepared pan.

Bake 25 to 30 minutes or until wooden pick inserted in center comes out clean and surface is lightly browned.

Cool completely; cut into bars.

Place remaining 2 tablespoons milk chocolate chips, remaining 2 tablespoons peanut butter chips and shortening in small microwave-safe bowl.

Microwave at HIGH (100%) 30 seconds; stir. If necessary, microwave at HIGH an additional 15 seconds at a time, stirring after each heating, until chips are melted and mixture is smooth when stirred.

Drizzle over bars. About

Heat oven to 350 F.

Melt butter in 13x9x2-inch baking pan in oven.

Combine crumbs, cocoa and sugar; sprinkle over butter.

Pour sweetened condensed milk evenly on top of crumb mixture.

Top with chocolate chips and toffee bits, then nuts; press down firmly.

Bake 25 to 30 minutes or until lightly browned.

Cool completely in pan on wire rack.

Chill, if desired.

Cut into bars.

Store covered at room temperature.

Preheat the oven to 350°F (175°C).

Grease a 13x9x2-inch baking pan.

Place the butter in a large microwave-safe bowl and microwave on HIGH (100%) for 2 to 2½ minutes or until melted.

Stir in the sugar and vanilla extract.

Add the eggs one at a time, beating well after each addition.

Mix in the cocoa powder until well blended.

Add the flour, baking powder, and salt, stirring until fully incorporated.

If using, fold in the chopped nuts.

Pour the batter into the prepared baking pan and spread evenly.

Bake for 30 to 35 minutes, or until the brownies begin to pull away from the sides of the pan.

Let the brownies cool completely in the pan on a wire rack.

Frost if desired, then cut into bars and serve.

Heat oven to 350°F.

Grease 13x9x2-inch baking pan.

Add boiling water; stir until mixture thickens.

Add flour, vanilla and salt; blend completely.

Stir in chocolate chips.

Pour into prepared pan. 3.

Bake 35 to 40 minutes or until brownies begin to pull away from sides of pan.

Cool completely in pan on wire rack.

Frost if desired.

Cut into squares.