In a bowl, mix the flour, powdered sugar, and salt.

Add the cold vegan margarine, cut into pieces, and rub it into the flour with your fingertips until it resembles coarse sand.

Add the cold water, one tablespoon at a time, and form a ball of dough. Avoid kneading too much to keep the pastry tender.

Wrap the dough in plastic wrap and refrigerate it for 30 minutes.

Preheat the oven to 180°C (350°F).

Roll out the dough on a lightly floured surface and line it into a tart pan. Prick the base with a fork.

Cover the pastry with parchment paper and baking weights (or dried beans) and bake for 15 minutes.

Remove the weights and parchment, then bake for an additional 5 to 10 minutes until golden. Let it cool completely.

Break the chocolate into pieces and place it in a heatproof bowl.

Heat the plant-based cream until it just starts to simmer, then pour it over the chocolate. Let it sit for 2 minutes.

Stir gently until the mixture is smooth and fully combined. Add the maple syrup (if using) and a pinch of salt.

Pour the ganache into the cooled tart shell and smooth the surface with a spatula.

Toast the hazelnuts in a dry pan or in the oven at 180°C (350°F) for 5 to 7 minutes until golden and fragrant.

Allow them to cool, then rub them between your hands to remove the skins (optional).

Scatter the roasted hazelnuts over the still-warm ganache, and optionally sprinkle with a pinch of flaky sea salt for a gourmet contrast. Alternatively, add some chocolate chips for extra decoration.

Place the tart in the refrigerator for at least 2 hours to allow the ganache to set.

Remove it 15 minutes before serving to fully enjoy its smooth and creamy texture.

Variations: Add a touch of spice, such as cinnamon or chili powder, to the ganache for a unique flavor twist.

Storage: This tart keeps well for 3 to 4 days in an airtight container in the refrigerator.