Prepare the Onions ahead of time - leftovers can be frozen or stored for later use, but you want to prepare these in bulk for convenience and best results.
Add Onions, melted butter, sugar and vinegar to the pot of your slow cooker and mix until evenly coated and well combined.
Set the cooker to low for 8-10 hours (overnight). Season with salt and pepper once complete. If there is too much liquid remaining, turn up the heat to reduce until thick and syrupy - stirring frequently to ensure they don't burn.
Prepare the white sauce by melting butter and flour in a saucepan over low-medium heat and whisking to form a paste. Let the paste cook for about a minute before gradually stirring in the milk, whisking continually to ensure no lumps form. Continue whisking and cooking until the sauce thickens and season with salt & pepper to taste.
Preheat oven to 180oC
Use the slicing disc of a food processor, mandolin or sharp knife to finely slice the potatos.
Layer the potatos, caramelized onions and white sauce in a deep baking dish - finishing with a layer of sauce and topping with grated cheese.
Bake in the preheated oven for approx 45mins until the potato layers are soft and the cheese topping is golden. Allow to stand & cool at least 20mins before serving.
0 servings
* The % Daily Value (DV) tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.