Caramalize thinly sliced onions and chopped garlic in EVOO [make sure onions and garlic are nice and dry when you put them in the heated EVOO or you’ll have problems getting carmalization!]
Melt butter in bottom of gratin/baking dish.
Combine salt and pepper with flour, and sprinkle a tbsp over each layer as you assemble.
Layer onions/garlic, thin sliced/peeled potatoes, and cheeses
Pour chicken stock and half and half on top after last layer assembled.
Top with more cheese and sprinkle with thyme.
Bake, covered, at 400 degrees for 50 minutes until cooked through, then remove cover and brown and bubbly on top.