For the flatbread dough – whisk together flour, yeast, salt, and sugar in a bowl. Add yogurt or milk and stir with your hands or a wooden spoon until it comes together into a shaggy dough. Turn dough out onto a floured surface and knead until dough is smooth and springs back when poked, about 5 minutes.
Place back into the bowl and cover with plastic wrap. Let rise in a warm place until doubled, about 2 hours.
Turn dough out onto a floured work surface. Cut dough into 8 even pieces. Roll each piece into a ball and place on a floured rimmed sheet pan at least 1 inch apart. Cover with a clean kitchen towel and let rise again for 2 hours, until doubled.
Meanwhile, heat 1 tablespoon of oil over medium high heat and sauté Vidalia onions until soft and slightly caramelized. Set aside.
Prepare a charcoal grill or use a gas grill.
Remove 4 pieces of dough and place onto a plate covered with a kitchen towel. Refrigerate the rest of the dough.
Preheat 12-inch cast iron pan. When hot, lightly brush with oil. With your hands or a rolling pin, stretch a piece of flatbread dough into an oblong shape about 10 inches long and 6 inches across.
Place into the cast iron pan and cook without moving until charred in spots and light golden brown, about 3 minutes.
Flip, and immediately begin adding toppings: drizzle with olive or pecan oil, salt and pepper, spread about 1 tablespoon of ricotta cheese, leaving a crust around the edge, scatter blue cheese crumbles, a handful of sautéed onions, dollop 3 teaspoons pepper jelly, and scatter a handful of arugula.
Close lid and let cook about 2 minutes more to wilt arugula slightly and melt cheese.
Remove flatbread with large heatproof spatula and place onto a plate to serve. Repeat with 3 more of the dough pieces.
Cut each flatbread into slices and serve.
Cook off the rest of the flatbread for later use. Let cool completely, place into a gallon size plastic bag and freeze for best results.