In a food processor (or if you don't have one of those, a large mixing bowl and a pastry knife), blitz butter, shortening, sugar, flour, and salt until the butter and shortening is about pea sized. Pour in ice water and mix until just combined. Transfer to a clean countertop and shape into a disc. Wrap with plastic wrap and let chill in the fridge for at least an hour.

Once chilled, remove from fridge and roll out until Â1/4 inch thick, thinner if possible. Use a glass or cookie cutter to cut circles to fit into your cupcake pan. Use a fork to poke holes in the bottom to prevent air bubbles. Bake at 325ºF for about 10 minutes. The crust will shrink a little bit, depending on your pan, so give it about Â1/2 inch to shrink down to. Remove from oven and set aside.

In a small pot, combine white sugar, maple syrup, flax mixture, butter, and stir over medium low heat until sugar is dissolved (about 5 minutes). Turn off heat, stir in vanilla extract and pecan pieces, and spoon mixture into to the par-baked tart shells. Be careful to not overfill and give the mixture room to bubble up without overflowing.

Bake for about 20-25 minutes, until the edges of the tart shells are lightly golden. Remove from oven and let cool on wire rack. If any of the pecan sugar mixture leaked out, you might have to gently separate the tarts from the pan using a knife.