1-Preheat oven to 350°F (175°C). Grease an 8-inch square baking pan or line it with parchment paper. The overhang helps lift bars out later. This sets you up for smooth sailing.

2-In a large bowl, cream together the 1/2 cup butter at room temperature, 1/4 cup granulated sugar, and 1/2 cup packed brown sugar. Mix until light and fluffy, about 2 minutes by hand or mixer.

3-Beat in 1 large egg and 1 teaspoon vanilla extract until smooth.

4-In a separate bowl, whisk 1 1/3 cups all-purpose flour, 3/4 cup graham cracker crumbs, 1 teaspoon baking powder, and 1/4 teaspoon salt.

5-Add dry mix to the butter mixture. Stir on low or by hand just until combined. Do not overmix, or bars get tough.

6-Divide dough in half. Press one half into an even layer on the bottom of the prepared pan. Use damp fingers for easy pressing.

7-Place 2 king-size chocolate bars (or 4 regular) over the dough. Break as needed to fit snugly. They melt into a rich layer.

8-Spread 1 1/2 cups marshmallow creme evenly over chocolate. A spoon or offset spatula works best. Do not worry if it is sticky.

9-Take remaining dough. Form into small disks, flatten, and arrange over marshmallow to cover. Or roll between parchment paper and flip onto top for even coverage. Press gently to seal edges.

10-Bake 25 to 35 minutes, until top is lightly browned. Ovens vary, so check at 25 minutes. Center sets but stays gooey.

11-Let cool completely in pan, about 1-2 hours. This firms chocolate and marshmallow for clean cuts. Speed up in fridge after 30 minutes room temp.

12-Cut into 16 bars. Warm briefly 10-15 seconds in microwave before serving for extra gooeyness.