- Vegetable oil cooking spray
- 6 ounces pancetta, cut into 1/8-inch-thick slices
- 1/2 cup (1 stick) unsalted butter, at room temperature
- 2 cups (8 ounces) shredded Monterey Jack cheese
- 2 cups (8 ounces) shredded mild Cheddar
- 1 teaspoon kosher salt
- 1 tablespoon vegetable or canola oil, plus extra, as needed
- 2 packed cups coarsely chopped baby spinach
- 16 (1/3-inch-thick) slices country-style white bread
Put an oven rack in the center of the oven. Preheat the oven to 400 degrees F.
Spray 2 baking sheets with cooking spray. Lay the pancetta in a single layer on the prepared baking sheets and bake until crispy and brown, about 12 to 14 minutes. Drain on paper towels. Cool for 5 minutes and crumble. Set aside.
In a food processor, combine the butter, cheeses, salt, and 1 tablespoon vegetable oil. Blend until smooth, adding extra oil, as needed, until the mixture is spreadable. Add the spinach and pulse until just combined.
Preheat a panini maker. Spread the cheese mixture over 8 slices of bread. Top with the crumbled pancetta. Put the remaining bread slices on top. Grill the sandwiches, 2 at a time, until golden and crispy, about 3 to 4 minutes. Cool for 2 minutes, then cut each sandwich in half and arrange on a platter.