Skip the scallions and just add more onions to the recipe. Since both are added to cook in the IP, scallions are just redundant flavor wise, extra expense and work. I also use chicken thighs instead of tenders.
I solved the watery sauce problem by reducing the broth to 1/2 cup. Also add the heavy cream AFTER cooking with the shredded cheese. I added a block of cream cheese at this step. This meant I didn't have to add any flour/butter to thicken the sauce. My family of 5 thought it was delicious. We have eaten it with rice and/or tortillas. I have also made enchiladas by removing and shredding the chicken thighs and putting the chicken in tortillas with a bit of sauce, more shredded cheese and then topping the enchiladas with the sauce before baking. The rest of the sauce we use for dipping tortilla chips in.