Line 2 baking sheets with parchment paper; set aside. In a small bowl, beat the 3 egg yolks and the heavy cream; set aside.
Three hours before you are ready to serve, remove the thawed croissant dough from the refrigerator. Lightly dust a work surface with flour and use a rolling pin to flatten the dough into a 26x18-inch rectangle about 1⁄8 inch thick. Use a straight edge and a paring knife or pizza cutter to trim about 1 inch from all 4 sides so that you have an even, 24x16-inch rectangle. Cut the rectangle into twenty-four 4-inch squares. Transfer to the prepared baking sheets; refrigerate for 30 minutes.
Place 2 oven racks at least 3 inches apart in the center of the oven, and preheat to 400°. Set a large baking dish filled with water on the floor of the oven. Retrieve the pastry squares, and if shrunken slightly, stretch and trim them back into even 4-inch squares. Use a 2-inch round biscuit cutter to punch holes in the center of half of the squares (these will be the top sides of the pastries). Brush the edges of the remaining dough squares lightly with egg wash (reserve the remaining egg wash for later). Layer the pieces with the cutouts onto the uncut pieces, then distribute them around the prepared baking sheets, leaving as much space between them as possible. Set the trays in a warm, preferably humid place and let the pastries rise until they are puffed and nearly doubled in size, 35-40 minutes.
Brush the tops of the danish evenly with the remaining egg wash. Put a few pieces of chopped bacon into each hole, reserving half, and divide the kimchi into each. Transfer the trays to the oven and bake until the pastry is quite golden and puffed slightly in the center but still soft, 18–20 minutes. Remove the trays. Working quickly, use the back of a spoon to lightly press the center of the pastry back down, deepening the hole. Carefully crack 1 egg into each hole and top with the remaining bacon bits. Immediately return the trays to the oven and bake until the pastries are deep golden brown, the egg whites have set, and the yolks are still tender and soft (about 9 minutes for a very runny yolk and 13–15 for well done). Remove, sprinkle each yolk lightly with chives, and serve immediately.