Preheat the oven to 400-F (200 C). Line a baking sheet with parchment paper.
Lay the puff pastry on a work surface and cut into 3-inch (7.5 cm) equal-sized squares or rectangles. It’s okay if they’re a bit bigger; just try to make them even.
Combine the melted butter, Dijon, Parmesan, and parsely in a small bowl. Brush or spoon a bit of this mixture onto the pastry square on the diagonal.
Sprinkle about 2 tablespoons (30 mL) of cheddar on top of the mustard-butter mixture.
Lay a folded slice of ham on top of the cheddar.
Fold the turnover by lifting one of the empty corners and laying it over the ham, then lift the opposite corner over and press it down onto the first corner to create a turnover.
Brush the top of the pastry with the egg wash, then transfer it to the prepared baking sheet.
Repeat until all of the puff pastry squares have been filled.
Bake on the parchment paper lined baking sheet for about 20 minutes until puffed up, lightly golden brown, and flaky.
Let cool, garnish with fresh parsley, then dig in!