Preheat broiler to high for a few minutes. Place the poblanos, tomatoes, onions, garlic and serrano onto large baking sheet. Drizzle lightly with olive oil. Broil for 10 to 12 minutes, turning over halfway through cooking time. Place poblanos in a plastic bag, paper bag or simply wrap in a clean kitchen towel to steam. Let ingredients cool.
Add dried ancho peppers to a saucepan and cover with water. Bring to a boil, reduce heat and cook for 6 to 7 minutes. At the same time, preheat 4 tablespoons of olive oil to medium heat for 5 minutes. Fry the diced potatoes until golden and crisp in most spots. Drain potatoes onto a plate lined with paper towels.
Peel the garlic. Add garlic, tomatoes, onion, serrano and drained chile ancho from saucepan. Add 1 cup chicken broth, blend on high until smooth, set aside.
Heat a large pot to medium/high heat. Add the beef. Season with 1 1/2 teaspoons each of the salt, pepper and garlic powder. Cook until nicely browned. Drain out any excess fat. Add sauce from blender, all remaining spices and reserved cup of broth. Peel, clean and slice the poblanos into small strips. Add the poblanos and potatoes to the picadillo. Stir well to combine and cook to reduce and thicken, about 20 minutes. Taste for salt and pepper. let cool before using it for empanadas. Yields 8 to 10 servings.