Helpful hint: For easy transfer later (and quicker cleanup too), roll and assemble the stromboli bombs or mini calzones on a piece of parchment paper. To prevent slipping, I tape the corners of the parchment paper to the counter. Lightly sprinkle your work surface and the rolling pin with flour to prevent sticking. The flour is helpful even when using parchment paper.
Prep the oven and pan: Preheat the oven to 400˚F and lightly coat a baking sheet with cooking spray or line it with parchment paper. Alternatively, a pizza stone may be used. Tip: A light sprinkle of cornmeal may be used on the parchment or stone. It will prevent sticking and add a hint of extra texture to the strombolis and calzones once cooked.
To assemble: In a small bowl beat the egg. Working with 1 dough ball at a time, press the dough into a flat disk and then use a rolling pin to roll it into a 6-inch round with a thickness of about ⅛-inch.
Spread a thin layer of Dijon over each of the rounds (about ½ teaspoon). Next, layer the meat evenly over the rounds, followed by the cheese, and any optional ingredients, leaving a ½-inch border so you can seal them. (Tip: If you’re making calzones, you can layer the ingredients on one half of the dough round to make folding over easier.)
For mini calzones: Fold the dough over to form a half moon shape, pressing the edge to seal. Crimp the edge with a fork and place the calzone on the prepared baking sheet.
For mini-strombolis: To seal mini-strombolis, fold two opposing sides of the dough rounds towards the center and pinch them together. Bring the other two sides in and pinch them to seal, making the seal as flat as you can. Place the mini-strombolis on the prepared baking sheet with the seam sides facing down.
Prep-ahead tip: At this point, I have covered and refrigerated for up to 4 hours.
Top and bake: Brush all the mini strombolis or calzones with the egg wash, and then cut 3 slits in the top of each one. Sprinkle with dried Italian seasoning or oregano or sesame seeds, and/or a pinch of coarse salt. A dusting of Parmesan is another option.
Bake for 12 to 15 minutes, or until the tops are lightly golden. Serve with warm marinara or pizza sauce for dipping, if desired.
Storage: Store cooled leftovers in an airtight container in the refrigerator for up to 5 days.
To reheat, remove the stromboli or calzones from the refrigerator 20-30 minutes before reheating to bring to room temperature. Wrap loosely in foil and place on a baking sheet. Bake in a preheated 350℉ oven for 12-15 minutes or until warm.
To make ahead and freeze: Cool the baked strombolis or calzones completely, and then tightly wrap each one individually in plastic wrap. Transfer to a plastic bag or airtight container and freeze for up to 3 months. For most even warming, thaw before reheating.