Preheat the oven to 375°F (190°C). Position a rack in the center of the oven for even browning.
In a medium bowl, combine the shredded mozzarella, sharp cheddar, and grated Parmesan. Mix gently so the cheeses are evenly distributed.
Add the cooked spinach and minced garlic to the cheese mixture. Season with salt and pepper to taste. Stir until everything is evenly combined; the mixture should be slightly sticky and hold together.
Line a baking sheet with parchment paper. This prevents sticking and helps the crisps brown nicely.
Use a small cookie scoop or a tablespoon to scoop small amounts of the mixture onto the prepared baking sheet. Space each scoop about 2 inches apart to allow for spreading. Flatten each mound slightly with the back of the spoon so they form thin rounds.
Bake for 10 to 12 minutes, watching for the edges to turn golden brown and the centers to set. The crisps will look bubbly and slightly darker at the edges when ready.
Remove from the oven and let the crisps cool on the baking sheet for 3 to 5 minutes. This allows them to firm up and become crisp. Gently transfer to a cooling rack or serving plate and enjoy warm or at room temperature.
Notes
Store cooled crisps in an airtight container lined with paper towel for up to 3 days. They’re best eaten within the first 48 hours for optimal crispness.