In a medium bowl, whisk together 3 egg yolks, 2 whole eggs, 1 cup of sugar, ⅓ cup of cornstarch, and ½ teaspoon of salt until fully combined and smooth. In a saucepan over medium heat, warm 2 ½ cups of whole milk and 1 ¾ cups of heavy cream until just steaming but not boiling. Gradually pour the hot milk mixture into the egg mixture while whisking constantly to temper the eggs, then stir in 7 oz of chopped dark chocolate until melted and smooth.

Preheat your oven to 325°F (160°C). Pour the chocolate custard mixture into a greased baking dish and place it in a larger baking pan. Fill the outer pan with hot water until it reaches halfway up the sides of the custard dish, creating a water bath. Bake for 45–50 minutes or until the custard is set but still slightly jiggly in the center. Remove from the oven and cool at room temperature.

While the custard is baking, prepare the tart base. In a mixing bowl, combine 1 cup of all-purpose flour, ⅓ cup of icing sugar, ¼ cup of cocoa powder, and ¼ teaspoon of salt. Mix in 1 stick of melted butter and ½ teaspoon of vanilla extract until a dough forms. Press the dough evenly into a tart pan and prick the bottom with a fork. Blind-bake at 350°F (175°C) for 15–20 minutes or until crisp, then allow to cool.

Once both the chocolate custard and tart base are completely cool, pour the custard over the tart base, smoothing the top with a spatula. Gently brush the surface with 1 tablespoon of your chosen jam for a beautiful glossy finish. Chill the assembled French chocolate flan in the refrigerator for at least 4 hours, or overnight if possible, to enhance the flavors and allow for easy slicing.