Preheat your oven to 400°F (200°C).
In a large skillet, cook the bacon over medium heat until crispy. Remove and let drain on paper towels.
Add the diced onions to the skillet and cook in the bacon fat for about 5 minutes, or until translucent.
Add the diced potatoes to the skillet and cook, stirring occasionally, until golden and tender, about 10-12 minutes.
Crack the eggs into a mixing bowl and whisk until thoroughly combined. Season with salt and pepper.
Fold in the crispy bacon and shredded cheese into the egg mixture.
Pour the egg mixture over the potatoes and onions in the skillet, gently stirring to combine.
Transfer the skillet to the preheated oven and bake for 20-25 minutes or until the frittata is set and golden.
Remove from oven and let cool for a few minutes before slicing and serving.
Garnish with chopped chives if desired before serving.