In a large skillet, cook the bacon over medium heat until crispy. Remove and drain on paper towels.

In the same skillet, add the diced potatoes and chopped onion. Cook until the potatoes are tender and golden, about 10-12 minutes.

In a mixing bowl, whisk together the eggs, milk, salt, pepper, and chives.

Preheat the oven to 350°F (175°C).

Add the cooked bacon back into the skillet with the potatoes, then pour the egg mixture over the top. Sprinkle with cheddar cheese.

Cook on the stovetop for about 5 minutes until the edges start to set, then transfer to the oven.

Bake for 20-25 minutes until the frittata is puffed and set in the center.

Let the frittata cool for a few minutes before slicing. Serve warm or at room temperature.