1/2 medium onion, finely diced
1/2 cup shredded, cooked brussels sprouts
1/2 cup shredded, cooked cabbage (optional)
1/2 cup grated carrots (can be cooked or raw)
2 cups leftover mashed potatoes
Salt and pepper to taste
Fried eggs, to serve (optional)
Gently heat the butter and oil in a wide, shallow skillet over medium heat, and add the onion. Cook for five minutes, until the onion is softened.
Turn up the heat to medium-high and add the shredded brussels sprouts, cabbage (if using), and carrots. Season with a little salt and pepper. Cook for five minutes, until the vegetables start to color.
Add the mashed potatoes to the skillet and stir briskly, until the vegetables and potatoes are well combined. Season again, to taste.
Press down on the skillet and fry for five to seven minutes, until the bottom is lightly browned and crisp. Drizzle a little oil around the edges if the mixture looks like it's drying out. The potato mixture should start making squeaking sounds at this point.
Using the lid of the skillet, invert the bubble and squeak into the lid, then slide back into the skillet to cook the other side. Cook for an additional five to seven minutes. Serve cut into wedges and topped with fried eggs, if desired.