Ingredients
6 tbsp. butter
¾ lb. white, cremini, or stemmed shiitake mushrooms, sliced
2 large shallots or 1 medium onion, finely chopped
1 large stalk celery with leafy top, finely chopped
2 large cloves garlic, finely chopped
Salt and 1 tsp. finely ground white or black pepper
¼ cup flour
½ cup white wine or 1/3 cup dry sherry
1 cup chicken stock
1 cup whole milk
1 bag (12 oz.) wide egg noodles
1 cup (loosely packed) mixed fresh dill, chives, and flat-leaf parsley leaves, finely chopped
½ cup sour cream or crème fraîche
1 rounded tbsp. Dijon mustard
½ cup frozen peas
2 cans (5 to 6 oz. each) sustainable tuna, drained and flaked
1 ½ cups crushed potato chips (about 3 oz.)
1 cup grated Parmigiano-Reggiano (about 4 oz.)
¼ cup chopped drained cornichons
Directions
Step 1
Bring a large pot of water to a boil for noodles.
Step 2
Preheat the broiler. Or position a rack in the center of the oven and preheat to 450°.
Step 3
In a large skillet or pot, melt the butter over medium-high heat. When it foams, add the mushrooms and cook, stirring occasionally, until browned, about 5 minutes. Reduce heat a bit. Add the shallots, celery, and garlic. Season with salt and 1 tsp. pepper. Cook, stirring often, until the vegetables soften, about 3 minutes. Add the flour and stir to coat the vegetables. Add the wine and cook until absorbed, about 30 seconds. Whisk in the stock and bring to a bubble. Add the milk and cook until the sauce thickens and reduces by about a third, about 3 minutes.
Step 4
Meanwhile, salt the boiling water and add the noodles. Cook until the noodles are almost tender, about 5 minutes. Reserve 1/2 cup of the cooking water, then drain the noodles.
Step 5
Add half the herbs, the sour cream, and Dijon to the sauce. Stir in the peas and cook until heated through, about 1 minute. Fold in the tuna. Add the noodles and toss until coated, adding the cooking water if needed to thin the sauce. Transfer to a 3-quart casserole dish.
Step 6
In a large bowl, mix the potato chips and Parm. Scatter over the casserole. Bake until the top is browned and the cheese melts, about 2 minutes. Top with the cornichons and remaining herbs.