This crispy, cheesy, meaty croissant showcases Dijonnaise (equal parts mayonnaise and Dijon mustard), one of the test kitchen's favorite condiments. It's also an easy way to enjoy leftover ham.
Preheat oven to 375 degrees. Cut a pocket in the croissant. Spread mayonnaise and mustard in pocket. Stuff with ham and cheeses; place on a baking sheet. Bake until cheese melts, 10 to 12 minutes; serve.