1 tablespoon vegetable oil
12 ounces smoked kielbasa sausage, diced
2 tablespoons butter
3 tablespoons flour
1 cup milk
1 cup chicken stock
1 pound potatoes, peeled and thinly sliced with a mandoline or knife
8 ounces cheddar cheese, shredded
salt and pepper, to taste
Preheat the oven to 350 degrees.
In a large, heavy-bottomed skillet, heat the vegetable oil over high heat. Add the kielbasa in an even layer, and cook until browned on all sides. Remove from the skillet and set aside.
Pour off the fat and strain it, then return it to the same skillet, set over medium-low. Add the butter and the flour and whisk together until a thick paste forms, about 1 minute.
Add the milk by the quarter-cupful, whisking well after each addition to incorporate. Cook until the sauce is quite thick, then add the chicken stock in the same way.
Remove from the heat and add half of the cheese to the sauce. Season the sauce with salt and pepper, to taste, and set aside.
Spread a ladleful of sauce into the bottom of a 1-quart oval baking dish, then top with a layer of sliced potatoes, and then a layer of kielbasa. Cover with sauce and continue until all of the ingredients are used up. Finish with a layer of sauce.
Bake, covered, for 40 minutes.
Remove from the oven and add the reserved cheese. Return to the oven, uncovered, and bake for an additional 30 minutes, or until the potatoes are tender and the cheese is nicely browned.
