Preheat broiler or set oven to 400 degrees F.
Place the spinach in a food processor with garlic, butter, salt and pepper and cheese and process, scraping the mixture down if necessary.
Halve bread lengthwise and slather it with spinach butter. Broil or bake to crisp, 3 minutes under broiler, 6 to 7 minutes in hot oven.
Cut into large cubes and serve with pasta.