Spray a large deep skillet with nonstick cooking spray and heat over medium.
Add the finely diced onion, minced garlic, and ground turkey to the skillet; season with salt and pepper and cook, breaking the meat apart, until the turkey is no longer pink.
Stir in the taco seasoning, Rotel (including juices), chicken stock, and the broken spaghetti pieces; cover and bring to a boil.
Reduce heat to a simmer, cover, and cook until the spaghetti is softened but still al dente, about 7 minutes.
While the pasta cooks, whisk together the evaporated milk and flour until smooth.
When the spaghetti is al dente, pour in the milk-flour mixture and cook, stirring, until the sauce thickens.
Stir in the grated cheese, corn, and chopped green onions until the cheese melts and ingredients are heated through.
Divide the mixture into four portions and serve immediately.
