Preheat the oven to 350°F (175°C).
Cook the egg noodles according to package instructions until al dente. Drain and set aside.
In a large skillet, melt the butter over medium heat.
Add the chopped onion and cook for 3-4 minutes until softened.
Stir in the minced garlic and chopped jalapeños and cook for an additional 1-2 minutes until fragrant.
In a large mixing bowl, combine the condensed cream of mushroom soup and whole milk. Stir until smooth.
Add the cooked onion, garlic, and jalapeño mixture to the soup mixture.
Fold in the drained tuna, thawed peas, shredded cheddar cheese, salt, and black pepper. Mix until well combined.
Add the cooked egg noodles to the mixture and gently stir to combine everything evenly.
Transfer the mixture into a greased 9×13-inch baking dish and spread it out evenly.
In a small bowl, mix the breadcrumbs and grated Parmesan cheese together.
Sprinkle the breadcrumb mixture evenly over the top of the casserole.
Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and the casserole is bubbly.
Remove from the oven and let it cool for 5 minutes before serving.