Ingredients
2 tablespoons unsalted butter
3 tablespoons all-purpose flour
3/4 cup low-sodium chicken broth
1/2 cup whole milk
Coarse salt and freshly ground pepper
1 tablespoon extra-virgin olive oil
1 pound sweet Italian sausage, cut into 1/4-inch coins
3 Cubanelle peppers, thinly sliced (about 5 cups)
1/4 cup white-wine vinegar
2 pounds russet potatoes (about 3 large), peeled and shredded on large holes of a box grater
3 ounces cheddar, shredded (1 cup)
6 scallions, chopped (1 cup)
Preparation
Preheat oven to 350 degrees with rack in upper third. Melt butter in a saucepan over medium-high heat. Whisk in flour; cook, whisking, 1 minute. Slowly whisk in broth and milk; bring just to a boil, whisking constantly. Remove from heat; season sauce with salt and pepper.
Heat oil in a skillet over medium-high heat; cook sausage until browned, about 2 minutes a side. Transfer to a 9-by-13-inch baking dish, scattering evenly.
Reduce heat to medium, add peppers to skillet, season with salt, and cook until browned and softened, about 7 minutes. Add vinegar; cook 30 seconds more, scraping up browned bits. Spoon evenly over sausage in dish.
In a bowl, combine potatoes, cheese, scallions, and sauce. Add to baking dish in an even layer. Cover with parchment-lined foil. Bake 40 minutes, then uncover and turn oven to broil; cook until top is well browned, about 8 minutes. Serve warm.
