1 tablespoon cornstarch
1 1/2 cups + 2 tablespoons whole milk
3/4 cup granulated sugar
1/2 cup creamy unsweetened peanut butter
1/4 teaspoon kosher salt
1 teaspoon vanilla extract
12 graham cracker squares, crushed
In a small bowl, whisk together the cornstarch and 2 tablespoons of milk to make a slurry. Set it aside.
In a medium saucepan, whisk together the remaining milk, sugar, peanut butter, salt, and vanilla, and heat over medium heat, whisking often. When it begins to steam, whisk in the cornstarch slurry and continue whisking for a few minutes until the mixture thickens slightly and coats the back of a spoon.
Remove it from heat and let cool for 10 to 15 minutes, whisking occasionally.
Stir in about half of the crushed graham crackers and spoon into 6 (3-ounce) paper cups (see Recipe Note). Place popsicle sticks into the centers and freeze until firm, about 5 hours.
Place the remaining crushed graham crackers in a bowl. Working one at a time, rip the paper cups away from popsicles, roll them in the graham crackers, and place them back in the freezer on a plate until you’re ready to serve.