Place a large pot of salted water over high heat and bring to a boil. Once boiling, add the egg noodles and cook to al dente, with a little bite left to them.
While you are waiting for the water to come to a boil, place a large skillet over medium heat and heat EVOO. Add onion or shallot to the oil and cook for 3-4 minutes, then add butter to the pan and melt. Once the butter has melted, sprinkle the flour in the pan and stir, letting the butter-flour mixture cook for about 1 minute.
Whisk in the stock and let the liquid cook until it thickens up, about 5 minutes. Add the half-and-half or milk and the mustard and bring the mixture back up to a bubble. Turn to low and add in the tarragon and the tuna; stir in the peas. Season the sauce with salt and pepper, to taste.
Drain noodles and combine with sauce, adjust seasonings and serve.
This is one of many “Yum-o!” recipes – it’s good and good for you. To find out more about Yum-o!, Rachael’s nonprofit organization, go to www.yum-o.org.