Preheat oven to 350 F (177 C).
In a medium sized mixing bowl, combine the almond flour, tapioca flour, xanthan gum, and salt.
Once the dried ingredients are well distributed, add the egg white and melted butter. Mix until combined and a dough has formed.
Roll the dough into a ball and wrap with plastic wrap. Set aside for 30 minutes.
While the dough relaxes, make your Mushroom Duxelles. Finely chop the mushrooms, until they are very finely diced. This can also be done in a food processor. It's not uncommon for me to use a cheese grater for mushrooms, also. The idea is to get the mushrooms very very small, but not a puree.
In a pan over medium heat, melt your butter. Add your garlic and onions. Sweat them until they are aromatic and starting to become translucent. About 2 or 3 minutes.
Add the chopped mushrooms to the pan. Add a flavorful amount of salt and pepper to this mixture. Also add half of your fresh sage.
Cook the mushrooms for about 5 minutes, or until all the water begins to release from the mushrooms. The mixture will become almost "soupy". At this point, add your red wine.
Continue to cook the mushrooms, until they are almost a paste. Set aside to cool.
Grease a sheet of parchment or wax paper. Place the doughball in the center of the paper. Grease a second sheet and place it above the dough. Roll the dough out until it is about 1/8-inch thin (3.2 mm).
I have two small Teflon pans (12-cups each), which I used for this. However, this could just as easily be done in a traditional 9-inch (23 x 4 cm) pie pan. For the smaller pan, using a large cookie cutter or the lid for a round food container or bowl (something that is slightly larger than the diameter of the mini pie/tartlet pan). Test one before cutting all your rounds. Be certain the size is correct. Then, using your cookie cutter or other round object as a guide, cut out roughly 20 small tartlet rounds. Combine the remaining dough, roll it out again and cut out at least four more rounds.
Grease the mini pie mold. Gently press each dough round into the mini pie mold.
Place a heaping teaspoon (7 mL) of the duxelles into the base of each tartlet cup.
Add 1/2 tsp (5 mL) of chopped dried cranberries to the tartlets.
Add 1 tsp (5 mL) of bacon bits to the tartlets.
Add 1 1/2 tsp (8 mL) of crumbled goat cheese to the tartlets. Season with a small dash of salt and pepper.
Bake the tartlets until golden, roughly 25 minutes. Garnish with a small blast of fresh sage.