1) Preheat the oven to 400°F. Get out several large baking sheets; no need to grease them.
2) Whisk together the flour, salt, pepper, and Parmesan.
3) Add the cold butter, working it in until no large pieces remain; a mixer works well here.
4) With the mixer running (or stirring all the while), drizzle in milk until the dough comes together; you may not use the entire 1/2 cup.
5) Gather the dough into a ball, and squeeze it a few times to bring it together. Divide it into three pieces. If you have a scale, they'll weigh about 6 1/2 ounces (187g) each.
6) Working with one piece of dough at a time, flatten it into a rough square, and place it on a lightly floured work surface. Roll the dough 1/8" thick; it'll be about 10" square (or an 11" circle, if your rolling efforts result in a circle).
7) Transfer the dough to a piece of parchment or aluminum foil. Using a sharp knife, pizza cutter, or pastry wheel, cut the dough into 1" squares; don't separate them. You may trim the edges first, if you like, in order to separate the "good looking" crackers from the raggedy ones around the edges.
8) Lift the piece of parchment/crackers onto a baking sheet. Sprinkle the crackers with coarse sea salt, additional grated cheese, and/or dried herbs, if desired.
9) Repeat with the remaining pieces of dough.
10) Bake the crackers for about 15 minutes, until they're a medium golden brown. Remove them from the oven, and cool right on the pan.
11) When the crackers are cool, store them airtight at room temperature.
Yield: about 200 small (1") crackers.