1. Position the rack in the lower third of the oven. Preheat the oven to 350°F. Butter and flour a 9 X 13-inch baking pan; set it aside.

2. Place the brownie mix, beaten eggs, melted Butter, and milk in a large bowl; stir with a wooden spoon until smooth, then pour into the prepared pan. Bake for 30 minutes, or until a toothpick or cake tester comes out with a few moist crumbs attached.

3. The moment the pan is out of the oven and on a wire rack, sprinkle the marshmallows over the top, followed by the nuts and the chocolate chips. Cover the pan with aluminum foil to hold in the heat for 5 minutes; then uncover the pan and cool for an additional 30 Minutes.

4. Cut the brownies into 24 pieces while they're still in the pan. Carefully remove them with an offset spatula. Serve immediately,or let cool completely before covering tightly with plastic wrap for storage at room temperature for up to 4 days. The brownies can also be tightly wrapped in wax paper, sealed in a freezer-safe bag, and frozen for up to 3 months; allow them to thaw at room temperature before serving.

To Vary this Recipe:
Substitute chopped pecans for the walnuts.

Instead of the semisweet chocolate chips, you can substitute:

• Butterscotch chips
• milk chocolate chips
• mint chocolate chips
• peanut Butter chips
• white chocolate chips

and/or stir any of the following flavorings into the batter with the milk:

• 1 tablespoon vanilla extract
• 2 teaspoons rum extract
• 2 teaspoons ground cinnamon
• 1 teaspoon almond extract