For the dough, place the butter in the freezer for 10 minutes to firm up. Then grate the butter into a bowl and place in the fridge while you measure the other ingredients.
Combine the flour and salt in a food processor. Add the chilled grated butter. Pulse for a few seconds and then add the water. Continue to pulse until the dough comes together slightly. Remove from the food processor and hand-knead to bring it all together. Do not overwork the dough; it’s okay if some of it flakes off. Pat the dough into a square about 2 inches thick. Wrap with plastic wrap and place in the fridge to relax for 30 minutes.
While the dough is relaxing, start the tart filling. Preheat the oven to 350°F.
Melt the chocolate in a microwave (see note #1) and set aside. In the bowl of a stand mixer fitted with the paddle attachment, cream together the brown sugar, butter, vanilla and salt, until light and fluffy.
Beat in the eggs, then the cream and maple syrup, followed by the raisins. Add the melted chocolate and stir to fully combine. Set aside in the fridge until you are ready to use (see note #2).
Take the brisée dough out of the fridge and lightly dust the dough and your work surface with flour. Roll out the dough to ⅒ inch thick. Using a 4½-inch cookie cutter, cut out rounds.
Spray a standard-sized muffin tin with nonstick spray, then line the wells with the brisée rounds. Leave about ¼ inch of dough above the rim. Place the muffin tin in the freezer for 10 minutes to relax the dough, so it does not shrink when baking.
Take the filling out of the fridge and give it a stir to reincorporate. Remove the lined muffin tin from the freezer and fill the tarts, using a 1-ounce ladle or #30 black (1 oz) ice-cream scoop.
Bake the tarts in the preheated oven for 20 minutes. Let cool completely, then remove from the muffin tin.