Preheat oven to 350F (175C). Arrange an overlapping layer of thinly sliced potatoes in bottom of lightly greased 9 in. by 13 in. baking pan.
Place over potatoes: a few thinly sliced onions, about 2 oz of Gorgonzola, about 1 Tbsp. of flour and the butter. Sprinkle with 1 tsp. thyme, ½ tsp. salt and pepper and about ½ cup cream. Repeat process until all the ingredients are used.
Cover pan with foil and bake for 1 hour.
Remove foil and bake another 20 to 30 minute or until the potatoes are soft and a golden crust forms.