Buckwheat Crêpes with Caramelized Onions

Name: Buckwheat Crêpes with Caramelized Onions
Ingredients: 1 cup whole milk , plus more as needed; 3 1/4 ounces buckwheat flour (about 3 1/4 ounces); 1/2 cup all-purpose flour (about 2 1/8 ounces); 1/2 cup water; 2 large eggs; 1 tablespoon unsalted butter , melted, plus more for skillet; 1 teaspoon kosher salt; 3 tablespoons unsalted butter; 3 tablespoons extra-virgin olive oil; 3 large sweet onions , thinly sliced (about 10 cups); 1/3 cup (2 2/3 ounces) Shaoxing wine or sake; 1 tablespoon white miso; 1 1/2 teaspoons gochugaru or crushed red pepper; 1/4 cup unsalted butter (2 ounces), divided; 8 large eggs; 1/2 teaspoon kosher salt , divided; 3/4 cup crème fraîche , divided; 4 teaspoons furikake , divided