For a more dramatically browned, bakery-style cheese top, once the pasta is fully cooked you can carefully lift the slow cooker insert out of the base (if your insert is oven-safe) and place it under a preheated broiler for 3 to 5 minutes, watching it extremely closely the entire time, until the cheese is deeply golden and beginning to blister beautifully. Set it on a heatproof surface and allow the casserole to rest for at least 10 minutes before serving so it can set slightly and become easier to scoop.
To serve, use a large spoon or spatula to scoop the baked mostaccioli straight from the slow cooker, making sure to dig all the way down through the layers to capture plenty of melted cheese and saucy pasta in each portion. The cheese should stretch as you lift it, and the pasta should be generously saucy without being soupy or watery.
Variations and Tips for Making It Your Own
Because this recipe is intentionally stripped down to just four core ingredients, it adapts beautifully once you have made the original a few times and feel comfortable with the basic technique.
For extra richness and a texture that moves very close to a lazy slow cooker lasagna, stir half a cup to a full cup of ricotta cheese into the middle layer alongside the mozzarella and Parmesan. This does technically add a fifth ingredient, but it makes the dish feel even more indulgent and special without any additional work.
