Best Tuna Noodle Casserole

Ingredients (18)

• + 1 (12 ounce) package egg noodles add to pantry
• + 4 ¼ teaspoons kosher salt, divided add to pantry
• + 4 tablespoons salted butter, divided add to pantry
• + 5 teaspoons olive oil, divided add to pantry
• + 1 (8 ounce) package sliced fresh mushrooms add to pantry
• + 1 small white onion, minced add to pantry
• ✓ ¼ cup all-purpose flour
• + 2 cups milk add to pantry
• + 1 ½ cups chicken stock add to pantry
• ✓ 2 tablespoons lemon juice
• + 1 teaspoon Dijon mustard add to pantry
• ✓ ½ teaspoon ground black pepper
• + 1 ½ cups shredded white Cheddar cheese add to pantry
• + 1 cup frozen sweet peas add to pantry
• + 2 (6 ounce) cans tuna, drained add to pantry
• + 1 cup panko bread crumbs add to pantry
• + ¼ teaspoon ground paprika add to pantry
• + 2 tablespoons finely chopped fresh parsley add to pantry