Preheat the oven to 350°F (175°C). Mix graham cracker crumbs with melted butter and press into the bottom of a springform pan. Bake for 8-10 minutes, then let cool.

Beat cream cheese until smooth, then add sugar, sour cream, lemon juice, and vanilla extract. Mix in eggs one at a time; do not overmix.

Pour filling into the crust. Prepare a water bath by placing the springform pan in a larger roasting pan filled with hot water halfway up the sides. Bake at 325°F (165°C) for 60-75 minutes.

Turn off the oven and let the cheesecake cool inside for an hour. Move to room temperature, then refrigerate for at least 6 hours.

Whisk egg yolks with granulated sugar; add cornstarch. Heat milk until hot, then temper the egg mixture with it. Cook until thickened and cool completely.

Spread cooled pastry cream over the cheesecake evenly.

Sprinkle sugar over the pastry cream and use a kitchen torch to caramelize it until golden.