Preheat oven to broil. Place poblano chile peppers on a cookie sheet and place in oven. Allow skin to blacken and blister, turning the chile peppers until all sides are done. (Note: Do not overcook.) When they are done, place them in a paper bag and seal. In about 15 to 20 minutes, take them out of the bag and peel the skin off each one under running water. Remove the stems and seeds.
In a blender, combine the chile peppers, broth, salt and pepper to taste and nutmeg. Blend until smooth. In a small saucepan over medium heat, warm the milk and set aside. In another saucepan over medium heat, melt the butter or margarine, add the flour and stir well. Add the warmed milk and stir until well blended. Add the chile pepper mixture and mix well. Reduce heat to low and simmer for 30 minutes.