Wash and slice the russet potatoes into 1/4-inch rounds, and cut the yellow onion into 1/2-inch thick wedges. Grate the garlic cloves and set aside. Cut the bacon into 1-inch pieces. Light your charcoal grill and let it heat until you have medium-high heat with good coals established—this typically takes 15-20 minutes. I find it helps to arrange your grill grate about 4-6 inches above the coals for proper heat control during cooking.

Place a large cast-iron skillet directly on the grill grate over the hot coals. Add the bacon pieces and cook for 5-7 minutes, stirring occasionally, until the bacon is crisp and has rendered its fat. Remove the cooked bacon with a slotted spoon, leaving the bacon fat in the pan—this flavorful fat is the base of your dish. Set the bacon aside on a paper towel-lined plate.

Add the olive oil and butter to the bacon fat in the skillet, allowing them to heat together for about 1 minute until the butter is fully melted and the mixture is sizzling. Immediately add the grated garlic and cook for 30-45 seconds, stirring constantly, until fragrant—this prevents the garlic from burning. I like to keep the heat brisk here to quickly infuse the fat with garlic flavor without overcooking it.

Add the sliced potatoes and onion wedges to the skillet, stirring to coat them evenly with the oil and fat mixture. Sprinkle with kosher salt, black pepper, and red pepper flakes, then stir well to distribute the seasonings. Cook over medium-high heat for 40-50 minutes, stirring frequently (every 5-7 minutes) to ensure even cooking and prevent sticking. The potatoes are done when they're golden brown on the edges, tender when pierced with a fork, and the onions are soft and caramelized.

Return the cooked bacon to the skillet and add the fresh thyme leaves (stripped from their sprigs). Stir everything together and cook for another 2-3 minutes, allowing the bacon to warm through and the thyme to release its aromatics. Taste and adjust the seasoning with additional salt and pepper as needed. Use a spatula to gently break up any large potato pieces while stirring if needed for consistent texture.

Transfer the hobo potatoes directly to serving plates or bowls while hot, or keep the skillet on a trivet at the table for a family-style serving presentation. The dish is best enjoyed immediately while the potatoes are crispy on the outside and creamy on the inside.