Prep Time: 5 minutes | Cook Time: 20 minutes
Cook the bacon and onion in a skillet large enough to serve from until they are cooked through and the bacon is almost crispy.
Add the leftover vegetables and mashed potatoes. Season with salt and pepper, if desired, then stir to evenly mix everything.
Cook until browned on the bottom, about 8-10 minutes. Flip it and cook the other side until browned.
Flipping tip: Cover the skillet with a large plate, then turn the skillet and plate upside down. The Bubble and squeak should come out onto the plate. Then, slide it back into the skillet, upside down.
(If using leftover boiled or roasted potatoes, it won't be as cohesive. It'll still taste good, it will just be more like a crumble than a cake.)
This dish works perfectly with any sort of leftover vegetables you have. The name comes from the traditional use of cabbage (since it bubbles and makes squeaky noises while it cooks), but feel free to swap it for anything from carrots to kale.