To make Subway flatbread, prepare the ingredients: two tablespoons of sugar, one teaspoon of salt, one cup of warm water and one tablespoon of active dry yeast. Also prepare three tablespoons of milk, a quarter of a cup of butter and six cups of flour.
Set aside a bowl, and add the sugar, yeast and water together. Mix it and allow to sit until it is frothy, and then add the milk and salt. Stir in three cups of flour, and mix carefully until the mix becomes creamy. Slowly add in more flour, mixing until you create a soft dough. Once the dough consistency is achieved, remove the mix from the bowl, and set on a floured surface.
Knead the dough on the surface for five minutes, and allow it to rest for five minutes. Once set, divide the dough into eight pieces and flatten the pieces, first with your hands and then with a floured rolling pin. The pieces should be a quarter of an inch thick. Once they are ready, heat up a grill pan over a high heat and cook the pieces until they are crispy brown on each side, which should take approximately two to three minutes of cooking.