In stand mixer bowl, with paddle attachment, mix both flours, sugar, and salt on slow speed for about 30 seconds.
Add the butter and combine with the flour on low to medium speed for about 1 minute.
Add the liquid and mix the dough on low to medium speed for 40 seconds to 2 minutes, or until it looks like gravel, depending on the temperature of the ingredients.
At this point, if the dough is still powdery, and looks like grated Parmesan cheese, pinch a piece to see if it comes together. If it falls apart, add 2 more tablespoons of liquid; if it holds together, keep mixing. If at any point, the dough no longer feels cold, place in refrigerator or freezer for 15 minutes.
Mix the dough on low to medium speed for 1 to 4 minutes, until it clumps together into a cohesive mass.
Flatten and roll the dough into a 6" square.
Cut into 12 pieces. Chill while you're making the filling.
To Make the Filling
Put all the ingredients into the bowl of a food processor. Pulse until mixture is smooth, about 5 to 6 times; don't over process.
Empty into measuring cup with a spout.
Assembly
Preheat oven to 375 degrees Fahrenheit.
Roll each piece of dough into a ball in your palms (lightly flour if necessary).
Put one ball into the center of each of 12 muffin cups. With a lightly floured wooden tamper, or similarly sized utensil, press the wider end (about 1" wide) into the center of the ball of dough until it thins and begins coming up the sides of the cup, then twist the tamper slightly to release it. You can also use your fingers or a flat-bottomed glass, lightly floured, to shape the dough up the sides of the muffin cups. Smooth the edges. Chill for 10 minutes to firm the dough.
Pour the filling into the dough-lined cups.
Bake until pastry is golden brown, about 30-35 minutes.
Let cool on wire rack for 10 minutes, then run a thin knife around the tartlets to loosen, and let them cool until firm enough to handle.
Using the tip of a small knife, lift the tartlets from the pan and set on a wire rack to cool.
If desired, garnish with whipped cream and a thin strip of orange zest.
