Step 1

Preheat oven to 350F. Line an 8-by-8-inch baking pan with aluminum foil, spray with cooking spray; set aside.

Step 2

In a large, microwave-safe bowl melt the butter, about 1 minute on high power.

Step 3

Wait momentarily before adding the egg so you don’t scramble it. Add the egg, brown sugar, vanilla, and whisk until smooth.

Step 4

Add the flour and stir until just combined, don’t overmix.

Step 5

Add the graham crackers and any crumbs on cutting board, marshmallows, chocolate chips and fold to incorporate.

Step 6

Turn batter out into prepared pan, smoothing the top lightly with a spatula.

Step 7

Bake for about 20 to 22 minutes, or until bars have firmed up in the center and edges will be set. Some marshmallows may have developed a hint of golden color. Allow bars to cool in pan for at least 30 minutes before slicing and serving. Bars will keep airtight at room temperature for up to 1 week, or in the freezer for up to 6 months.