Preheat the oven to 410 (F).
In a Pyrex-type, oven-safe, glass bowl, combine 6 tablespoons unsalted butter, 1 tablespoon vegetable oil, 3 tablespoons water, 1 tablespoon sugar, and a pinch of salt. This is going to sound weird, but place the bowl in the preheated oven for 15 minutes, until the mixture is boiling and the butter starts browning.
After 15 minutes, remove from the oven, and add 1 cup of flour quickly spooning in flour in 1 tablespoon sized chunks. Use a heatproof rubber spatula to stir in the flour until it pulls off the sides of the bowl. The mixture is gonna bubble and smoke, but trust the recipe! This will result in the most delicate crust you will ever eat. Once the dough is cool enough to touch, divide the ball of dough into four 5-inch tartlet pans. Use the back of your hand to flatten out the dough onto the bottom of one tartlet pan, and your finger tips to mold the dough up into the corners and sides of the tartlet pan. It's gonna feel really greasy and kinda unpleasant, but go with it. Use a fork to poke several holes into the crust. Repeat for the remaining tartlet pans.
Bake the tartlets at 410 (F) for 6 to 8 minutes, or until the crust is light brown and starts to appear flakey. This crust is very forgiving — it should have hardly any cracks.
At 15 minutes, remove the carefully from oven and let rest on a wire rack. Allow to cool completely; once it has cooled, the tartlets are ready for filling.