In a mixing bowl, mix together the water, yeast, vinegar, and sugar. Let stand for 5 minutes until the yeast begins to foam.
Add one cup of flour, the salt, and the oil. Continue adding one cup of flour at a time. Knead the dough until it comes together and becomes soft. The dough should be slightly sticky but not wet.
Let dough sit, covered with a moist towel until it doubles in size, or reaches the top of the bowl. If you have time, punch the dough down and let rise again. If you don’t have time, it’s okay to proceed to the next instruction.
Place the dough on a greased countertop. Cut dough in half. Grease a large cookie sheet with cooking spray and then sprinkle a thin layer of cornmeal on the bottom of the pan.
Roll each dough ball into a long rectangle or log shape and place onto the cookie sheet. Slice long slices vertically along the bread every few inches.
Beat the egg and brush a thin layer all over both loaves.
Cover the bread with saran wrap and let rise until doubled in size.
Once doubled, bake at 400 degrees for 20-25 minutes until golden brown or as dark as you like.