Heat oil in a large sauté pan over medium heat. Add onion and cook 8-10 minutes, until golden at the edges.

Add cold cuts and stir for 2-3 minutes. Add ketchup, mustard, and mayonnaise. Cook while stirring for 2 more minutes, until well-combined.

On a sheet of parchment paper, roll out the puff pastry to a sheet that’s as square as possible. Cut off the four corners so that you have a round sheet of puff pastry.

Add the filling to the middle, leaving a 2-3 inch border at the edges.

Fold over the edges of the dough while pinching into pleats, forming a circle.

Brush the crust generously with duck sauce. Sprinkle with Everything but the Bagel Seasoning. Galette can be frozen at this point. If serving immediately, bake for 35-40 minutes.