Carmelized Onion and Potato Flan

You will need:
onions
butter
potatoes
Gruyère cheese
salt and pepper

Pick your pan first.
I use a glass, straight sided flan dish - either a 9 inch to serve 4-6 people
or a 12 inch to serve 6-10 people. You can use a glass pie plate if
you don't have a flan dish.
Lightly butter the pan.
Slice 2-4 large onions. I usually cut them in half first and then
slice them lengthwise but you can use your prefered method. Just don't
chop them. You want nice onion strings.
Place onions in fry pan with 1-2 Tbsp. butter and saute slowly until
onions are a deep caramel
colour. This will take about 20 minutes.
Peel and slice 2-4 large potatoes. I use a mandoline and slice them
right into the flan dish.
Cover the bottom of the pan with potato slices - if you want to be
fancy you can overlap the slices in a spiral pattern - and sprinkle
lightly with salt and pepper.
Cover potatoes with 1/2 of the caramelized onions.
Grate Gruyre cheese over the onions
Repeat with another layer of potatoes, caramelized onions and Gruyre cheese.
Bake uncovered in 350 degree oven for about 50 minutes.
Cut into wedges and serve.

From MGCC blog...sounded wonderful!