Preheat the oven to 350ºF/175ºC. Lightly grease your casserole dish.
Slice the head of cabbage and chop the onion. Don’t cut too small – you want them to hold their shape as the casserole is cooking.If needed, shred the cheese.
Crush the crackers in a bowl or Ziplock bag with a rolling pin or heavy-bottomed glass. In a small pot or in the microwave, melt the butter. Mix the melted butter with the crackers until the mixture begins to stick together.
Cook the onion and cabbage
Heat the oil and the butter in a large, nonstick pan. Add the onion and cook for about 2 minutes. Add the cabbage, salt, and pepper and cook for a further 5-8 minutes, stirring frequently until the cabbage has wilted and partially cooked.
Assemble and bake
Transfer the cabbage mixture to the casserole dish. Add the soup, sour cream, and shredded cheese (save 1/3-1/2 of the cheese to top your casserole). Mix to combine and level off.
Top the casserole with the rest of the cheese and then cover with the cracker crust.
Bake at 350ºF/175ºCfor 30 minutes or until the topping has turned a golden brown color.
To make ahead or store
To make ahead: Precook the cabbage and combine the casserole ingredients as per the recipe but do not add the cracker topping yet. Once assembled, cover tightly and store in the refrigerator for two days or in the freezer for up to 2 months. When ready to bake, bring to room temperature (first, if frozen, let thaw in the freezer overnight, add the cracker topping, then bake as per the instructions.Store in the Fridge: Store leftovers in an air-tight container in the fridge. It'll keep for 3-4 days - and taste better after a day or two. To freeze: Allow the dish to come to room temperature before transferring it into a freezer-safe bag or airtight container. It’ll keep for up to 6 months.
Video
Notes
Seasoning: I think salt and pepper work well on their own, but if you want to vary the flavor or adapt to your tastes, try using garlic powder, ground cumin, paprika (smoky or sweet work best for this), dried thyme, cayenne pepper or chili powder in the mix or use dill or parsley to garnish.
Cheese: Cheddar cheese is great for melting, but you could use any hard cheese that melts well, like gouda, gruyere, Monterey Jack, mozzarella cheese, Swiss, or hard goat cheese.