S’mores bars with marshmallow meringue

Crust
Graham cracker crumbs	12 ounces
Butter, unsalted, melted	12 tablespoons
Sugar, light brown, packed	2 tablespoons
Salt, fine sea	¼ teaspoon
Brownie filling
Butter, cold, cubed	8 tablespoons
Chocolate, unsweetened, chopped	4 ounces
Sugar, granulated	1 ¼ cups
Vanilla extract	2 teaspoons
Salt, fine sea	¼ teaspoon
Eggs, room temperature	2 large
Flour, all purpose	½ cup
Meringue
Egg whites	3 large
Sugar, granulated	¾ cup
Vanilla extract	½ teaspoon
Cream of tartar	¼ teaspoon

1. Preheat to 350°F; line a 9-inch-square baking pan with foil, allowing 2 inches of overhang on two sides. 
2. In a medium bowl, using a fork, mix all of the crust ingredients until evenly moistened. 
3. Press the crumbs evenly into the baking pan. 
4. Bake for 8 to 10 minutes, until lightly browned. 
5. Let cool complete; leave the oven on. 
6. In a heat-proof medium bowl set over a saucepan of simmering water, melt 8 tablespoons butter with the chocolate over moderate heat, stirring occasionally, until smooth, about 5 minutes. 
7. Remove from heat, and whisk in the 1 ¼ cups sugar, vanilla, and salt. 
8. Whisk in the eggs until smooth, then stir in the flour until just incorporated. 
9. Spread the batter evenly over the cooled crust. 
10. Bake for about 25 minutes, until the edge is set but the center is still slightly jiggly. 
11. Transfer to a rack and let cool completely. 
12. Preheat the broiler. 
13. In a heat-proof medium bowl set over a saucepan of simmering water, whisk the egg whites with the ¾ cup sugar until the whites are warm and the sugar is dissolved, about 3 minutes. 
14. Transfer the mixture to the bowl of a stand mixer fitted with the whisk. 
15. Add the vanilla and cream of tartar, and beat at medium speed until firm 
16. Increase the speed to high, and beat the meringue until stiff and glossy, about 5 to 7 minutes. 
17. Mound the meringue on top of the filling, swirling it decoratively. 
18. Broil the meringue 8 inches from the heat until lightly browned, about 1 minute. 
19. Cut into bars, and serve. 

Recipe from Food&Wine Magazine, April 2015.