Step 1Prepare 18 coals without starter fluid in a chimney starter until they are hot enough to have formed a thin coating of white ash over the surface of each coal. Alternatively, the frittata can be cooked in a large cast iron or oven-proof nonstick skillet and baked in a conventional oven heated to 375 degrees.
Step 2Place a 2-quart (8-inch) Dutch oven over a hot bed of coals, and fry the bacon until the fat is rendered and the bacon begins to crisp, 6 to 8 minutes. Stir in the sliced onion and continue to cook, stirring frequently, until the onion is softened and beginning to color, an additional 6 minutes or so. Stir in the potato and cook 1 to 2 minutes to warm through.
Step 3In a separate bowl, beat together the eggs, half-and-half and chives, seasoning with one-fourth teaspoon salt and one-half teaspoon pepper.
Step 4Remove 12 coals from under the Dutch oven and leave the remaining 6 evenly spaced. Stir the egg mixture in with the bacon, onion and potato in the oven, and cover with the lid. Evenly space the 12 coals on top of the lid, and bake the frittata until the eggs are puffed and set, 15 to 20 minutes. If using a conventional oven, cook, uncovered, until the eggs are puffed and set, 15 to 20 minutes.
Step 5When the eggs are ready, scatter over the cheese, cover and cook until the cheese is melted, 2 to 3 minutes more. Serve immediately.