This is perfect as a dinner side, buffet, or brunch dish. It can be assembled a day ahead and baked later. It does take quite a bit of time to cook, so plan to get it in the oven first. If you have a mandolin or slicer, use it to make the potato slices evenly and quickly.
Serves 10 - 12
- ½ lb (226 gr) bacon, regular or low salt
- 1 shallot, peeled, minced
- 1 Tbsp butter
- 2 ½ cups half n’ half
- 2 tsp thyme
- 2 tsp salt, to taste
- ¾ tsp ground black pepper
- ½ tsp dry mustard powder
- 2 lbs (900gr) Yukon gold potatoes, peeled, cut into ⅛ inch thick rounds (keep in a bowl of water)
- 1 medium sweet onion, peeled, halved and thinly sliced
- 8 oz cheese, shredded (suggestions: old cheddar, swiss, smoked cheese gouda)
- 2 Tbsp flour
Preheat oven to 375°F/190°C. Butter 13x9 inch glass baking dish.
Cut up bacon with kitchen scissors into a frying pan over medium-high heat. Brown and drain on paper towels. In a small saucepan over medium heat, sauté shallot in butter until clear. Whisk in cream, thyme, salt, pepper, and mustard powder. Add less salt if using regular bacon; more salt if using low salt bacon. The potatoes absorb a lot of salt flavor. Remove potato slices from water and pat dry with paper towels.
Place ⅓ of the potatoes in the prepared casserole dish, overlapping slightly. Sprinkle with 1 tablespoon flour. Top with ½ of the onions, ½ of the crumbled bacon, and ⅓ of the cheese.
Layer with another ⅓ of the potatoes, tablespoon flour, remaining ½ of the onions, remaining ½ of the bacon and ⅓ of the cheese.
Top with remaining ⅓ of potatoes. Pour cream mixture evenly over potatoes. Sprinkle with remaining ⅓ of the cheese. Cover gratin with foil and bake for 1 hour. Uncover and bake until top is golden brown and potatoes are tender, about 45 minutes longer.
Let cool for 10 minutes before serving.