Step 1

Preheat the oven to 350 F.

Step 2

Process the end slices of the loaf of bread to fine crumbs in a food processor or blender, about 1/2 cup. Transfer to a large bowl, add the meat, cheeses, parsley, olive oil, egg, garlic, oregano, thyme, salt and pepper, and mix well with your hands to combine.

Step 3

Moisten your hands with cold water and roll the meat mixture into 1-inch balls; reserve on a baking sheet. Line another baking sheet with parchment or a silicone mat.

Step 4

Lay 2 slices of the bread on a clean work surface. Butter 1 side of each slice. Place 4 meatballs on one slice of buttered bread, top with a second slice, buttered-side down, and press firmly together. Use a serrated knife to cut off the crusts. (Reserve the crusts and bake separately for a "cook's treat.") Repeat with the remaining bread and filling. Cut each sandwich into 4 squares and transfer to the lined baking sheet. (This process can be done assembly-line style, lining up slices of buttered bread and assembling multiple sandwiches at a time.)

Step 5

Bake until the sandwiches are golden brown, 15 to 20 minutes. Transfer to a rack pan and let cool slightly. Serve warm.

Step 6

Excerpted from " Mother Sauce" by Lucinda Scala Quinn (Artisan Books).Copyright © Photographs by Mikkel Vang.