1. The Sauce
Heat 1 Tbsp. olive oil in saucepan over medium heat. Sauté 1 cup of the onion and 3 cloves of garlic in oil 5 to 7 minutes, or until soft. Add dried chilies, and sauté 3 minutes more. Stir in tomatoes and 2 cups of water. Season with salt and pepper, and simmer 10 to 15 minutes. Remove from heat, cool 5 minutes, then purée in blender or food processor until smooth.
2. The Enchiladas
Preheat oven to broil. Place poblano chiles on baking sheet, and broil 15 to 20 minutes, or until blackened on all sides, turning often. Cool in covered bowl, then peel off skins and remove seeds. Chop chiles into 1/4-inch pieces.
3. Preheat oven to 375°F. Heat 1 Tbsp. olive oil in skillet over medium heat. Sauté remaining onion and garlic in oil 3 to 5 minutes, or until soft. Transfer to mixing bowl, and add queso fresco, 1/2-cup Monterey Jack cheese, cilantro, and chopped chiles.
4. Spread tortillas on baking sheet. Warm 3 minutes in oven to soften.
5. Spread 1 cup sauce over bottom of 13x9-inch baking dish. Divide cheese mixture among tortillas, and roll loosely. Place filled, rolled tortillas in baking dish. Top with remaining sauce, and sprinkle with remaining Monterey Jack cheese. Bake 15 to 20 minutes, or until Sauce is bubbly and cheese is melted. Sprinkle with cilantro before serving.