Place the oven racks in the top third and the bottom third of the oven. Preheat the oven to 250F. Line 2 baking sheets with parchment paper. Using a glass or bowl as a guide, trace 6 circles, about 3½-inches in diameter, onto the parchement paper. Set aside.

Use an electric mixer to whisk the egg whites, cream of tartar and salt until they are frothy, about 1 minute. Gradually sprinkle in the sugar while the machine is running on high speed and beat until the meringue is glossy and stiff, about 3 minutes. Fold in the lemon extract.

Transfer the meringue into a piping bag with a large star tip. Pipe onto the circles on the parchment paper, starting at the center and working your way out.

Transfer to the oven. Immediately change the oven temperature to 200F. Bake for 45 minutes. Rotate the pans and cook an additional 30 minutes. Without opening the oven door, turn off the oven and let the meringues cool in the closed oven for at least 6 hours.

Let the ice cream soften slightly. Mix the graham crackers in with the ice cream.

Using a kitchen torch, (or the oven broiler - see tip in post above), brown the edges of of the meringues. Spread ⅓ cup of the graham cracker ice cream onto 6 of the meringues, and 2 tablespoons of lemon curd onto the other 6 meringues. Sandwich one of the ice cream topped meringues with one of the lemon curd topped meringues. Repeat with the remaining meringues. Serve immediately or freeze up to 2 hours.