01 -
Heat a skillet over medium-high heat. Add the diced kielbasa and cook until browned at the edges, 4-5 minutes. Transfer to a plate and cool completely.
02 -
Heat the oven to 400°F. Line two baking sheets with parchment paper. Lightly roll each puff pastry sheet to smooth the seams, then cut each sheet into 12 squares.
03 -
Spread about 1/4 teaspoon mustard in the center of each square, leaving the edges clean. Add a spoonful of cooled sausage, 1 or 2 cheese curd pieces, and a few chives.
04 -
Fold each pastry square over the filling to make a small parcel. Press the edges with a fork to seal and place seam side down on the prepared baking sheets.
05 -
Freeze the filled bites for 15 minutes. Beat the egg with 1 teaspoon water, brush the tops lightly, and sprinkle with flaky salt.
06 -
Bake for 18-22 minutes, rotating the pans once, until puffed and deep golden. Cool for 5 minutes, garnish with chives, and serve with mustard.