Sift the flour onto a clean work surface and form a well in the center. Cut the cold butter into medium cubes and add them to the flour.
Using your fingertips, gently rub the butter into the flour until the mixture looks sandy, with a few pea-size bits of butter remaining.
Add the kosher salt, sugar, baking powder, and yeast, and mix lightly to combine. Add a bit of milk, then the eggs, and start mixing. Remember, this is a shortcrust-style dough, not a yeast dough—you don’t want to knead it like bread.
Simply combine the ingredients until evenly mixed. Always add the liquid gradually—you might not need all of it. Continue mixing until the dough has a uniform color and smooth consistency.
This dough should not be elastic. Pat the dough into a rough square, transfer it to a plate, cover with plastic wrap, and refrigerate for 30 minutes. This resting time allows the butter to firm up again, making the dough easier to roll, cut, and bake later.
Once chilled, the dough will be firm, smooth, and slightly moist. Sprinkle a little flour on your work surface and a bit more on top of the dough, since it may have absorbed some moisture in the fridge.
Using a rolling pin, flatten the dough into a rectangle about 12 x 9 inches (30 x 23 cm), adding a light dusting of flour as needed to prevent sticking.
Lightly scrape the surface of the dough down the middle with your finger or a fork; this helps remove surface moisture and ensures that when folded, the layers adhere properly. If you skip this step, the bisquets may separate while baking.
Fold the right third over the center, scrape the surface again, then fold the left third over the top—like folding a letter. Rotate the dough 90 degrees and roll it out again to about ½ inch (1 cm) thick.
Using a lightly floured 4-inch (10 cm) round cutter, cut out the dough and place the pieces on a parchment-lined baking sheet, leaving space between each for even baking.
Using a lightly floured smaller 1-inch (2.5 cm) cutter, gently press the center of each round to create a small indentation—don’t cut all the way through, or you’ll end up with a doughnut! Continue cutting out bisquets, making as many as possible from one batch of dough.
Gather any scraps, bring them together gently, and chill briefly before re-rolling. Let the bisquets rest at room temperature for 45 to 50 minutes so the dough relaxes and the yeast activates slightly.
For the egg wash, beat one egg with a pinch of salt and a pinch of sugar. The salt helps break down the egg proteins for a smoother texture, while the sugar promotes caramelization and color.
Brush the tops lightly with the beaten egg, being careful not to let the egg wash pool in the center, which can cause an eggy flavor, or drip down the sides, as this can affect the rise.
Preheat the oven to 340°F (170°C) and adjust the rack to the upper-middle position. Bake for 25 minutes, or until puffed and golden brown.
Serve warm for the best flavor and texture.