1. Heat the broiler in the oven and set the oven rack so it’s 5-inches (12cm) from the heating element.
2. Set a cast iron skillet on the stove top over high heat and let it get very hot.
3. Shape the dough into 8-inch (20cm) rounds on a lightly floured surface, then working one-by-one, overturn the cast-iron skillet and carefully put a round of dough on the upturned bottom of the skillet, using your fingers to nudge the dough to the edges and being careful to avoid touching the very hot skillet.
4. Bake each round of dough individually under the broiler until each is lightly browned and “set” – they will only take a minute or two, so watch them carefully. As they come out of the oven, pry the dough off the pan (you may need to use a spatula if they stick a bit) and set each one on a wire cooling rack.
(You can also put the toppings on the raw dough, right before step #4, and bake the pizzas off to finish them.)
5. Brush each round of dough in the center with garlic oil, making sure to get some of the minced garlic on each round. Divide the onions over each round of dough, leaving a border, then top with potatoes and crumble blue cheese in large pieces over each pizza.
6. Run each pizza one-by-one under the broiler, on the overturned cast-iron skillet, then serve immediately.