- Preheat the oven to 400°F and lightly grease a 12-cup muffin tin. Pull the chilled dough from the fridge 20 minutes before rolling out.
- Cut each of the logs of chilled pie dough into six pieces. Roll each piece out onto a lightly floured work surface to just under six millimeters thick, and use a 12 centimeter round cookie cutter to cut each into a circle. Line each muffin cup with the pastry so that it comes about 12 millimeters higher than the muffin tin, and chill the lined tin while preparing the filling.
- Melt the butter and brown sugar in a saucepot over medium heat, stirring until the mixture is bubbling. Remove the pot from the heat.
- In a separate bowl, whisk the eggs with the maple syrup, lemon juice, vanilla and salt. Slowly pour the hot sugar mixture into the egg while whisking constantly until incorporated.
- Sprinkle a few pecan pieces (or walnuts, raisins or chocolate chips) into the bottom of each tart shells and ladle or pour the filling into each shell.
- Bake the tarts for ten minutes at 400°F, then reduce the oven temperature to 375°F and bake for an additional 10-15 minutes, until the filling is bubbling and the crust edges have browned.
- Cool the tarts in the tin. After about five minutes, carefully twist them around in the pan to prevent sticking leaving them in the pan to cool completely.
The butter tarts should be stored in the fridge, but are best served at room temperature. The tarts can be stored chilled for up to three days.
For the dough:
- Stir the flour, sugar and salt to combine in a bowl or using a stand mixer fitted with the paddle attachment. Cut in the butter by hand with a pastry cutter or on in the mixer on low speed until just small pieces of butter are visible and the mixture as a whole takes on a pale yellow colour (indicating that the butter has been worked in sufficiently).
- Stir the water and lemon juice together and add to the dough, mixing until the dough just comes together. Shape the dough into two discs, wrap each and chill for at least two hours before rolling. Alternatively, the dough can be frozen for up to three months and thawed in the fridge prior to rolling.