2 tablespoons olive oil
2 tablespoons butter
1/2 head green cabbage (about 1-1/2 pounds), shredded
1 onion, chopped in a medium dice
2 ribs celery, cut in a small dice
2 cloves garlic, minced
2 tablespoons fresh dill, chopped
2 teaspoons dry mustard
2 tablespoons lemon zest
Juice of 1 lemon
1-1/2 cups heavy cream
1-1/4 cups Parmesan cheese, grated, divided
2 5-ounce cans tuna, drained
1/2 cup frozen peas
Salt, to taste
Ground black pepper, to taste
Melt the butter and the olive oil together in a large cast iron skillet over medium heat.
Once the butter has melted, add the cabbage, onion, celery and garlic. Season with salt and pepper. Cook until the vegetables soften, about 10 minutes.
Add the dill, mustard powder, lemon zest and lemon juice.
Pour in the heavy cream and add 1 cup of Parmesan cheese. Cook, stirring regularly, until the cream and cheese have come together to form a sauce.
Continue cooking for another 5 minutes to allow the sauce to thicken.
Add the tuna and the frozen peas and stir to combine. Sprinkle the remaining Parmesan cheese over the top of the casserole.
Preheat the broiler and place the cast iron skillet into the oven for about 5 minutes, until the cheese on top has become golden and the casserole is bubbling throughout.