01 - Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper.
02 - In a medium mixing bowl, whisk together eggs, heavy cream, milk, salt, and pepper until fully blended.
03 - Add chopped cooked bacon, finely chopped red onion, shredded cheese, and chopped chives to the egg mixture and stir to combine.
04 - Place bagel halves cut side up on the prepared baking sheet. Spoon the egg filling evenly into the cavity of each bagel half.
05 - Transfer to oven and bake for 20 to 25 minutes or until the quiche filling is just set and golden on top.
06 - Allow the stuffed bagels to cool slightly before serving. Serve warm, with ketchup on the side if desired.