Peel, seed and cut bell peppers into thin strips. Thinly slice finger chile. In a skillet, heat oil over medium heat. Add bell peppers, finger chile and garlic and cook, stirring, until peppers are softened, about 5 minutes. Using a slotted spoon, transfer to a plate. Season to taste with salt and black pepper and set aside.
Add potatoes to pan, in batches. Spread first batch evenly across the bottom and cook for 1 minute. Move to 1 side of the pan and repeat with remaining batches of potatoes. Continue to cook potatoes, turning often, until evenly browned on all sides, about 10 minutes.
Return peppers to pan. Stir well to combine. Season to taste with hot pepper flakes (if using).
Using a slotted spoon, transfer potato mixture to a warm serving platter. Season to taste with additional salt and black pepper. Garnish to taste with parsley (if using). Serve immediately.