Step 1: Preheat your oven broiler to high. Place the poblano peppers on a baking sheet. Broil for 5-7 minutes per side, turning with tongs, until the skins are completely blackened and blistered. Alternatively, you can char them over an open flame on a gas burner or grill.
Step 2: Once blackened, immediately transfer the hot peppers to a heat-safe bowl and cover tightly with plastic wrap or a lid, or place them in a paper bag and close it. Let them steam for 10-15 minutes. This steaming process makes the skin incredibly easy to peel off. Once cooled enough to handle, peel away the charred skin, then slice the peppers open, remove the seeds and stems, and cut the flesh into 1/4-inch wide strips (rajas).
Step 3: In a large skillet or Dutch oven, heat a tablespoon of olive oil over medium heat. Add the sliced onion and cook, stirring occasionally, until softened and translucent, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Step 4: Add the roasted poblano strips to the skillet with the onions and garlic. Stir well to combine all the flavors. Cook for 2-3 minutes, allowing the flavors to meld. Season lightly with salt and freshly ground black pepper.
Step 5: Pour in the Crema Mexicana (or heavy cream). Stir gently to incorporate, ensuring all the rajas are coated. Bring the mixture to a gentle simmer, then reduce the heat to low. Continue to cook for about 5-7 minutes, stirring occasionally, allowing the sauce to thicken slightly.
Step 6: Stir in the shredded Monterey Jack or Oaxaca cheese until it is completely melted and gooey, creating a rich, homogenous sauce. Continue stirring until the cheese is fully integrated and the mixture is smooth and bubbling. Taste and adjust seasoning as needed.
Step 7: Serve hot, garnished with fresh cilantro or a sprinkle of paprika if desired. This dish is fantastic on its own or as a vibrant side to your favorite Mexican main courses.