Preheat the oven to 350°F (175°C).
Heat the oil in a Dutch oven or large skillet over medium-high heat. Add the chopped onion and minced garlic and sauté until the onion is tender, about 4–5 minutes.
Add the chopped cooked chicken, RO*TEL tomatoes and chiles, salt, and pepper. Bring to a boil, then reduce heat and simmer, stirring occasionally, for 15 minutes.
Remove the pan from heat and stir in the 2 tablespoons chopped cilantro and the crumbled feta or goat cheese. Taste and adjust seasoning if needed.
Spoon about 1/4 cup of the chicken mixture down the center of each tortilla, roll up, and place seam-side down in a lightly greased 13×9-inch baking dish.
In a small saucepan over low heat, whisk together the half-and-half and ground cumin until warmed and combined (about 1–2 minutes). Alternatively microwave until warm.
Pour the warmed half-and-half mixture evenly over the rolled tortillas in the baking dish.
Cover the dish with foil and bake for 10 minutes. Remove foil and bake 10 more minutes.
Sprinkle the shredded Monterey Jack and Cheddar cheeses over the enchiladas and bake uncovered for an additional 10 minutes, until cheese is melted and bubbly. Garnish with chopped cilantro if desired.
