Preheat the oven to 425 degrees.
Start by cooking the pasta according to the package instructions, leaving it very slightly al dente. Reserve one cup of pasta water. Then, drain well and set aside.
Heat a large pan over medium/high heat. Grease with cooking spray or a drizzle of olive oil.
Add the diced onions and cook for 1-2 minutes. Place the minced garlic into the pan. Cook for another minute or two, until fragrant.
Add the ground chicken and start breaking it up. Sprinkle on the seasonings and continue to breakup while cooking. Continue to break up and mix in the seasonings until the chicken is fully cooked. Remove from heat and set aside.
Reduce the heat to medium. Then, add the Velveeta cheese and begin to warm up the cheese. Continue to stir together and melt the cheese into the chicken.
Add the Rotel and stir together. Allow it to come to slight simmer, to heat up.
Spoon the drained spaghetti into the meat mixture and stir together. If needed, slowly add reserved pasta water, milk or sour cream (or yogurt or mayo).
Grease a casserole dish with cooking spray. Pour in the spaghetti casserole and evenly spread across the entire dish.
Top with the shredded cheese then bake in the oven for 5 minutes, or until the cheese is melted and bubbly.
Divide into four pieces, add your favorite taco toppings and enjoy.