In a stand mixer bowl or food processor, combine the flour, butter, salt, and black pepper. Process until the dough reaches a coarse crumb texture. Add the egg and milk, and continue mixing until the dough is fully combined. Transfer the dough to a work surface. Wrap it in plastic wrap and refrigerate it for 20 minutes.

Season the sweet potatoes and onion with salt, black pepper, and a touch of garlic powder. Roast them in a preheated oven at 355°F (180°C) until they are golden and tender. Let them cool for about 20 minutes.

Roll out the dough on a sheet of baking paper to a thickness of 1/2 cm (about 1/4 inch) and line a tart pan with it. Spread the roasted sweet potatoes and onions evenly inside the tart crust. Add the goat cheese on top.

In a small bowl, prepare the Royal Sauce by whisking together the sweet cream, eggs, and spices until the mixture is smooth and free of lumps. Pour it over the filling. Sprinkle pine nuts and almonds on top for decoration.

Preheat the oven to 390°F (200°C). Lower the temperature to 355°F (180°C) and place the quiche on the lower rack (not the lowest). Bake for about 35-40 minutes, until the edges of the crust are golden and the tart is sufficiently browned. Allow the tart to cool thoroughly before serving. Enjoy!