I bought 2 jars of white cheese sauce to make lasagne with the other day and had enough left over to try something without wasting the rest of the sauce. I made this and it worked. It's super easy and ready in 45 mins. You can add other ingredients such as onion, leek and herbs if you wish but I just used bacon this time.
3/4 jar of white cheese sauce
Upto 4 potatoes sliced thinly
4 unsmoked bacon rashers
Grated Cheddar cheese
Preheat oven to 180 degrees (fan)
Peel your potatoes and slice thinly (about 1/2 cm thick)
Cook your bacon in a frying pan to your preference.
Layer your potatoes in a oven proof dish and cover with half of the cheese sauce, if you think there isn't enough to cover you can add a little whole milk and stir to thin it out.
Cut up 2 bacon rashers onto your first layer randomly placing on top of the potatoes. Repeat steps 4 and 5 once more.
Place in the oven for 20 minutes
Remove from oven and sprinkle on the cheddar cheese and parmesan. Place back into the oven for a further 20 minutes.