In a food processor, pulse the flour, powdered sugar, and salt together until combined. Add the cold cubed butter and pulse until the mixture looks like coarse crumbs with some pea-sized pieces. Add the egg yolk and pulse a few more times.

Add ice water one tablespoon at a time, pulsing after each addition. Stop adding water as soon as the dough starts to come together when pressed between your fingers.

Divide the dough into 12 equal portions. Press each portion into the bottom and up the sides of a mini tartlet pan or a cup in a mini muffin tin. Aim for even thickness throughout. Prick the bottoms with a fork.

Place the filled pans in the fridge for 30 minutes. While the shells are chilling, preheat your oven to 375 degrees F.

Bake for 10 to 12 minutes, or until the edges and bottoms are lightly golden. Remove from the oven and let them cool completely before adding the filling.

Pour the fat-free evaporated milk into a small saucepan. Heat over medium-low heat until it just begins to simmer around the edges. Remove from the heat immediately. Add the chopped chocolate and let it sit undisturbed for one minute.

Stir the chocolate and milk together in slow, gentle circles until the ganache is completely smooth and glossy. Stir in the vanilla extract.

Spoon the ganache into each cooled tart shell, filling it nearly to the top. Set the tartlets on a flat tray and refrigerate for at least one hour, or until the ganache is fully set.

Carefully remove the tartlets from the pans. Serve as is, or top with fresh berries, a pinch of flaky sea salt, chopped nuts, or a small dollop of whipped cream.