Preheat oven to 375ºF (190ºF). Lightly spray a 9×12 inch casserole dish with cooking oil.

By hand or using a mandoline thinly slice potatoes and place in cold water. Set aside.

In a large skillet fry bacon on medium heat for about 5 to 6 minutes or just until starting to crisp. Remove bacon using a slotted spoon onto a paper towel lined plate. Discard all but 1 tbsp of the bacon drippings. Wipe skillet clean.

Melt butter combined with bacon drippings over medium heat. Add shallot and cook for about one minute. Add flour, stir constantly for about 1 to 1 ½ minutes until flour and butter mixture turns a golden brown.

Slowly add in both milk and cream whisking constantly until combined. Sauce should thicken slightly.

Add thyme, garlic and seasonings. Allow to simmer for about 5 to 8 minutes.

Add half the gruyere cheese, whisking until cheese has blended into sauce. Remove from heat. Remove thyme and garlic from sauce and discard.

Drain sliced potatoes into a large bowl. Add half the bacon to the bowl and pour sauce over top. Combine well to coat potatoes. Pour mixture into prepared casserole dish. Sprinkle remaining bacon over top. Seal top with tin foil and place on center rack of oven and bake for 1 hour.

Remove foil and pierce potatoes with a fork, if they are soft remove from oven and top with remaining gruyere and provolone. Return to oven and bake for an additional 15 mins or until cheese is golden and bubbling.

Allow to stand for 15 minutes before serving. Garnish with green onions or chives.

Notes:
Switch your cheese! Try using a combination of blue cheese and cambazola.