Preheat oven to 350 degrees and lightly grease a 2 quart baking dish.
Cook noodles according to package directions but do not overcook.
Meanwhile, in a large skillet or medium saucepan over medium heat, melt butter.
Add onion and seasonings, cooking until onions are translucent.
Stir in flour and cook 1-2 minutes, stirring continuously.
Gradually stir in milk/cream and continue to cook, stirring, until thickened.
Stir in mayonnaise, tuna and frozen peas, bring to a simmer and cook another minute or two. Taste and adjust seasonings.
Combine with cooked, well-drained noodles mixing well. Pour into prepared baking dish.
Top with shredded cheese, then crushed potato chips. Lightly sprinkle with black pepper and/or paprika if desired.
Bake 25-30 minutes or until casserole is bubbly and top is lightly browned.