Pre-heat oven to 350 degrees.
In a large pot, add water and 2 Tbsp of salt. Cook pasta according to package or till al dente.
In a large pot over medium heat, melt 3 tablespoons of butter. Add in onions and cook for 5 minutes or until they are soft. Add in garlic and 1 tsp of salt, pepper, and herbs and spices. Cook for a minute or until you can smell the garlic.
Turn the heat to low. Add in flour. Cook for 1-2 minutes. Stir constantly.
Add in your milk/heavy cream mixture in thirds. Stir constantly so you don't end up with a clumpy sauce or burnt cream.
Add in another 1 tsp of salt, pepper, and herbs and spices. Taste the sauce and adjust your seasoning. If you want it to have a little kick you can add red pepper flakes or a seasoning like slap yo mama. (My husband's favorite)
Once your sauce has thickened, add in your frozen peas and carrots and tuna. Ensure to break up your tuna. Turn off your heat and stir in 1/2 cup of cheese. Taste and adjust seasonings.
In a greased 9×13, add drained pasta. Top with your tuna sauce mixture. Stir till everything is combined. Top with the rest of the cheese. Bake for 25-30 minutes. Once it comes out of the oven, let it cool for 5-10 minutes.
Enjoy!
I love to top mine with sour cream and onion chips and extra cheese!