Ingredients

• 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

Instructions

1. Watch how to make this recipe.
2. Put an oven rack in the center of the oven. Preheat the oven to 400 degrees F.
3. 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.
4. 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.
5. 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.