Warm the oil in a heavy saucepan over medium heat. Add the chorizo and cook it for 2 minutes, or until the fat begins to melt. Add the onions and garlic. Cook until the chorizo is well browned. Drain off the grease. Add the tomatoes, poblano chile, and chicken stock. Bring the mixture to a simmer and slowly add the cheese, blending it with a spoon. As each batch of cheese has melts, add more, cooking over low heat. When the cheese has melted and the mixture comes together, it is ready to serve with warm tortillas or crispy chips. Keep warm while serving.