Preheat the Oven:

Begin by preheating your oven to 400°F (200°C). This step ensures that the Parmesan Onion Appetizer Squares will cook evenly, giving you the desired golden-brown crust. A hot oven is key to achieving that perfect contrast between the crispy bread and the creamy topping. While the oven is heating up, gather the rest of your ingredients and prepare your workspace. It’s helpful to have everything within reach to make the preparation process smooth and efficient.

Prepare the Parmesan Mixture:

In a medium-sized mixing bowl, combine the mayonnaise, grated Parmesan cheese, grated onion, salt, pepper, dried oregano, dried basil, and granulated sugar. Using a spatula or spoon, mix everything together until well combined. The mayonnaise acts as the binder, ensuring that all the ingredients stick together to form a creamy topping. The grated Parmesan cheese provides both flavor and texture, giving the mixture a satisfying richness. As you stir the ingredients together, you’ll notice how they start to form a smooth, cohesive mixture. It should have a slightly thick consistency, which will allow it to stay in place when spread onto the cocktail bread.

Prepare the Cocktail Bread:

Take the cocktail bread slices and arrange them on a clean surface. If you’re using a baking sheet, make sure it’s lined with parchment paper or a silicone baking mat to prevent sticking. You want to ensure that the bread slices fit comfortably on the baking sheet without overlapping. Using a tablespoon, scoop the Parmesan mixture and spread about 1 tablespoon of the mixture evenly over each slice of cocktail bread. The goal is to cover the bread with a generous layer of the Parmesan mixture, but not so much that it spills over the edges. Be sure to spread the mixture all the way to the edges of the bread for even coverage.

Arrange on a Baking Sheet:

Once the cocktail bread slices are topped with the Parmesan mixture, place them on a baking sheet in a single layer. It’s important that the bread slices are spaced out slightly to allow the heat to circulate evenly and cook the bread to a crisp. This will also help the topping cook and brown more evenly. Depending on the size of your baking sheet, you may need to use more than one sheet. If you’re making a larger batch, it’s fine to cook the squares in batches.

Bake to Perfection:

Place the baking sheet in the preheated oven and bake the squares for approximately 20 minutes, or until the Parmesan topping is golden brown and bubbly. The cooking time will depend on your oven, so be sure to keep an eye on them during the last few minutes to ensure they don’t overcook. The bread should be crisp and golden, while the topping should be bubbly and browned on top. The aroma that fills the kitchen as the Parmesan mixture bakes is simply irresistible, making the wait worthwhile.

Cool and Serve:

Once the Parmesan Onion Appetizer Squares are done, remove them from the oven and allow them to cool slightly before serving. These squares can be enjoyed hot, warm, or at room temperature, making them an excellent make-ahead option for parties or gatherings. If you’re not serving them immediately, you can store them at room temperature for a few hours or refrigerate them and reheat them in the oven before serving. They also hold up well, making them a great snack to have on hand for unexpected guests or late-night cravings.