These baked ham and cheese puff pastry croissants are the kind of recipe that looks impressive, smells incredible, and comes together faster than you'd expect.
Preheat oven to 425℉ and line a large baking sheet with parchment paper. Roll out the puff pastry to a 12" x 24" rectangle. Cut eight equal-sized squares out of the puff pastry, each square should be 6" x 6". Whisk the egg in a small bowl and set it to the side.
Spread 1 Tablespoon of Dijon mustard diagonally across each square of puff pastry. Evenly divide the cheddar cheese among the pastries, sprinkling it over the mustard in a diagonal line from corner to corner. Repeat with the Parmesan cheese. Roll each slice of ham into a loose log and place it on top of the cheese, following the diagonal.
Fold one corner of the puff pastry over the ham and brush the top of it with the egg wash (this acts as a "glue" that helps hold the puff pastry together while it is baking). Fold the opposite corner over top, making sure to overlap the pastry to enclose it, creating a snug "blanket" around the ham and cheese.
Evenly space the croissants on the parchment-lined baking sheet, leaving a good amount of space between each one (depending on the size of your baking sheet, you may have to use two). Brush all exposed puff pastry with the egg wash. Bake ham and cheese croissants for 20 minutes until golden brown and crispy. Top with diced chives and serve immediately.
Notes
Ham - Other options for meat include turkey, prosciutto, cooked bacon, or shredded chicken.
Cheese - Instead of cheddar cheese, you can use Gouda, Harvarti, Gruyere, or Swiss cheese.
Add extra fillings like caramelized onions, spinach, mushrooms, or asparagus.
Keep the puff pastry cool until you are ready to work with it. Allowing it to sit at room temperature for too long could result in the butter melting and the pastry not puffing up as it should.
Baking the croissants at a high temperature is key to achieving the signature "puff" of the pastry.
Gently seal the edges when wrapping up the pastries. Flattening the dough too much can cause the pastry not to rise as it should.
Store leftover baked ham and cheese croissants in an airtight container in the fridge for up to 4 days.
To make ham and cheese croissants ahead of time, prepare them and wrap the baking sheet with plastic wrap. Refrigerate for up to 24 hours before baking. Brush the tops with egg just before baking to prevent the pastry from getting soggy.