For the crust:
2 cups graham cracker crumbs
1/3 cup sugar
1 stick unsalted butter, melted
For the filling:
4 cups whole milk
3/4 cup sugar
5 extra-large egg yolks
1/3 cup cornstarch
1 tsp. salt
7 oz. bittersweet chocolate, broken
2 tbsp. unsalted butter, divided
1 tbsp. Kahlua liqueur
1 tsp. instant coffee powder
For the whipped cream:
1 cup heavy cream
2 tbsp. sugar
1 tsp. vanilla extract
1. Preheat the oven to 350 degrees F.
2. Combine the graham crackers, sugar, and butter in a bowl and mix well with a wooden spoon. Lightly press the mixture into an 11-inch metal tart pan with removable sides. Bake for 10 minutes and set aside to cool.
3. Heat the milk in a small saucepan until almost simmering.
4. In the bowl of an electric mixer fitted with the paddle attachment, combine the sugar, egg yolks, cornstarch, and salt and, with the mixer on low speed, slowly pour the milk into the bowl. Pour the mixture into a large saucepan and cook over medium-low heat for 5-10 minutes, stirring constantly with a wooden spoon, until mixture is very thick.
5. Off the heat, add the chocolate, butter, Kahlua, and coffee. Beat with a whisk until smooth and pour into the cooled crust.
6. Place plastic wrap directly on the chocolate filling and chill the tart for 6 hours, until cold.
7. Decorate with whipped cream and shaved chocolate and serve cold.
*From Ina Garten