In a large bowl, combine 1 cup flour, sugar, salt, and dry yeast. Add milk and softened butter or margarine. Stir in starter. Mix in up to 3 3/4 cups flour gradually, you may need more depending on your climate.
Turn dough out onto a floured surface, and knead for 8 to 10 minutes. Place in a greased bowl, turn once to oil surface, and cover. Allow to rise for 1 hour, or until doubled in volume.
Punch down, and let rest 15 minutes. Shape into loaves. Place on a greased baking pan. Allow to rise for 1 hour, or until doubled.
Brush egg wash over tops of loaves, and sprinkle with chopped onion.
Bake at 375 degrees F (190 degrees C) for 30 minutes, or till done.
