For the filling and crust:
1-1/2 cups whole milk
1/4 teaspoon table salt
3 large egg yolks
1/3 cup very firmly packed light brown sugar
4 teaspoons all-purpose flour
4-1/2 ounces (1/2 cup) creamy peanut butter (preferably natural, made with only peanuts and salt)
1/2 teaspoon pure vanilla extract
1 Press-In Cookie Crustbaked and cooled (I like chocolate or graham cracker for this tart)
For the glaze:
3 ounces bittersweet chocolate, finely chopped
2 ounces (1/4 cup) unsalted butter, cut into 6 pieces
1 tablespoon light corn syrup
Make the filling:
In a medium saucepan, bring the milk and salt to a simmer over medium heat, stirring occasionally. Meanwhile, in a small bowl, whisk the egg yolks, brown sugar, and flour until well blended. Slowly add the hot milk, whisking constantly. Pour the mixture back into the saucepan. Cook over medium heat, whisking constantly, until it thickens and comes to a full boil, about 3 minutes. Continue to cook, whisking constantly, for 1 minute. Remove the pan from the heat and add the peanut butter and vanilla; whisk until well blended.
Pour the hot peanut butter mixture into the crust and spread evenly with a rubber or offset spatula. Gently press a piece of plastic wrap directly on the filling’s surface to prevent a skin from forming. Refrigerate the tart until cold, about 2 hours, before proceeding with the recipe.
Make the glaze:
Melt the chocolate in a small bowl in a microwave or in a double boiler over medium heat (see How to melt chocolate). Add the butter and corn syrup and whisk until the butter is melted and the mixture is smooth, about 1 minute. Carefully remove the plastic wrap from the top of the chilled filling. Drizzle the glaze over the filling and spread it evenly to cover the tart completely. Refrigerate the tart in the pan until the glaze sets, about 30 minutes or up to 12 hours.