Beekman is famous for its Blaak cheese and with good reason. This semi-hard cheese, a 60/40 combo of goat and cow's milk has great nutty flavor and texture. Here it's grated and mixed with Beekman onion jam, a heady jam of onions, balsamic vinegar, and a touch of maple syrup. It all get wrapped in a flaky homemade dough. If you prefer, you can use store-bought puff pastry in place of the homemade dough-check the package for suggested cooking times and temps.
Pulse together the flour, sugar and salt in a food processor until combined. Add the butter and pulse until the mixture resembles coarse crumbs with some fat pea-size pieces. Add the yogurt and pulse until just combined and the dough holds together when pressed between your fingers.
Transfer to a sheet of plastic wrap, shape into a flat disk and refrigerate for at least 1 hour or up to 1 day. The dough can be frozen for longer storage up to 3 months.
Preheat the oven to 325 degrees F.
Let the dough sit until slightly softened (this makes rolling easier), 10 minutes. On a lightly-floured work surface roll the dough out to 1/4-inch thickness. Cut out 16 rounds using 3-inch round cutters (re-roll scraps if necessary). Mix together the cheese, onion jam and mustard. Spoon a level teaspoon of cheese filling onto half of each round, leaving a 1/2-inch border. Brush the border with egg-water mixture; fold the top over and pinch to seal.
Place 1 inch apart on a parchment-lined baking sheet and brush the tops with the egg-water mixture. Bake until golden brown and crisp, about 35 minutes.