In a large skillet, heat the olive oil and add the sliced garlic. Cook until fragrant, then remove the garlic with a slotted spoon and discard. Add the spinach to the oil with a pinch of salt and cook until just wilted. Remove the spinach to a strainer and allow to drain.
In a medium mixing bowl, whisk together the sour cream, milk, green onions, green chiles, a handful of shredded cheese, and the cumin and salt.
In a separate, larger bowl, combine the chicken, drained spinach, and about half of the sauce.
Spray the bottom of a 9x13 glass baking dish with non-stick cooking spray, and spread about a tablespoon of the sauce mixure in the bottom.
Fill each tortilla with about 2 tablespoons of the chicken mixture, and place in the glass baking dish seam side down.
Spread the sauce over the top of the rolled tortillas, then top that with the rest of the shredded cheese.
Bake at 350 degrees for about 30 minutes, until the cheese is melted and bubbly. Top with sliced green onion and cilantro to serve if desired.