Preheat the oven to 375°F (190°C).
Cook the egg noodles according to package instructions until al dente. Drain and set aside.
In a large oven-safe skillet or pan, heat olive oil over medium heat.
Add the chopped onion and cook for 3-4 minutes until softened.
Add the minced garlic and cook for 1 minute until fragrant.
Stir in the frozen peas and cook for 2 minutes until heated through.
In a medium bowl, whisk together the condensed cream of mushroom soup and milk until smooth.
Add the cooked noodles, soup mixture, shredded cheddar cheese, flaked tuna, salt, and black pepper to the skillet. Stir gently to combine all ingredients evenly.
Spread the mixture evenly in the pan.
Sprinkle the crushed potato chips evenly over the top of the casserole.
Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the casserole is bubbly and the topping is golden brown.
Remove from the oven and let it cool for 5 minutes before serving.