You can use this dough as the pastry base for just about any filling you desire. Pressing the dough into mini muffin cups is a fussy, finicky process, and I've tried methods other than just using my thumbs, with various degrees of success. One idea, which i just gleaned from Food52, a totally great cooking site, is to use some sort of tamper on top of plastic wrap. Genius! I have a tamper, but I've never liked it much because it tends to stick to the dough, and it's a pain to dip the tamper into flour each time and doesn't work all that well. So I plan to try out this idea the next time I make a batch and will update this summary then.
Using a hand mixer, stand mixer or food processor, mix the ingredients together into a soft, moist dough.
Form the dough into a ball and wrap in plastic. Refrigerate until firm, maybe 30 minutes. This step will help make the dough less sticky. (But if I use the helpful hint above with the plastic wrap, chilling the dough may be counter productive, as softer dough will be easier to tamp.)
Use your fingers to press a 1/2-ounce ball of dough into each mini-tart cup. Using that amount of dough per tartlet should give you 24, which is the standard amount per pan and the yield given for this recipe. I do use my digital scale, which takes very little extra time and insures that I get an even amount of dough for each shell. I have also started using some type of liner, either these tulip-shaped parchment ones or these white paper ones. (Be sure to note the larger size of the white ones--they're not the smallest size, 1 1/4", but 1 1/2".) Your life will be less fraught if you use some type of liner, as overfilling the shells by even a tiny bit makes them bubble up and over, and then you have a sticky mess.
If you're using the shells with a filling that needs minimal or no baking, then you need to pre-bake the shells. Prick the bottoms and bake at 350 for 15 minutes, then check for doneness--they should be a nice golden brown. You may need to use your temper to gently press down the bottoms if they've gotten puffy, as otherwise you won't have as much room for the filling as you'd have with a flat bottom.
If you're using a filling that needs to bake for the same amount of time as the shells, then of course you'll fill them first and then bake. Follow the directions for the individual filling recipe--you''ll probably need 25 minute at 350.