Mix all and cook. This can be made ahead and reheated
Refried beans; (if you prefer you can add this to the Hamburg mix)
Shredded sharp cheese
Lettuce; (all can be made ahead)
Picante sauce; green chili sauce, avocado dip or any other topping you can think of
This is the original recipe I submitted to Country Woman and won with
fry bread- mix flour with rest of ingredients and work to form a ball. If mix is a little dry add small amount more milk. Form two balls and set aside in covered bowl to rest. Leave at least one hour. Roll out on floured board to plate size. If they aren't rolling out too well lots of times I do the same as pizza dough by pulling to make them bigger and then finish rolling them. Use wax paper to separate each one. You can make as many as you wish but I have the best luck using the above mixture for each two people I am going to serve. They seem to rise better and are more uniform. At this point they can sit for awhile just be sure you have covered well with wax paper. To fry them I use a large cast iron skillet (any other skillet or deep fryer will work) with about 1/2 inch oil or enough so they can float a little. Be sure the oil is hot enough. They will fry fast so turn as soon as the bubbles on the bread pop up well, browning on the other side. Do not cook too long. Drain on paper towels. If you are serving a group arrange all the toppings on a table. Set the hot pan of meat first in line. Fry bread one at a time as directed above and let everyone serve themselves. Allow at least 1/3 lb Hamburg for each, as bread fills the whole plate and serving themselves they usually take that much.
I have served 30+ by myself and it worked well, but the one a group of us did for over 200 took several frying at once and a lot of prep work before. I don't recommend trying it!