-
1
Preheat the oven to 350F.
-
2
Cut the bacon into 3/8-inch-thick slices, and stack them in two piles, then cut the bacon crosswise into 3/8-inch even-sided rectangular shapes, or lardons.
-
3
Heat a large saute pan or Dutch oven over medium-high heat for a minute.
-
4
Swirl in the olive oil and add the bacon.
-
5
Cook the bacon about 5 minutes, stirring often, until tender and lightly crisped.
-
6
Remove to a plate with a slotted spoon, reserving the bacon fat in the pan.
-
7
Add the onions, 2 teaspoons thyme, 1 teaspoon salt, and some pepper to the pan.
-
8
Cook 15 minutes, stirring and scraping with a wooden spoon, until the onions start to caramelize.
-
9
Turn the heat down to low, and continue to cook, about 10 minutes, stirring often, until the onions are a deep golden brown.
-
10
Remove from the heat and set aside.
-
11
Use a mandoline to slice the potatoes into 1/16-inch-thick rounds.
-
12
Pour 1/2 cup cream evenly onto the bottom of a 9-by-9-inch (or equivalent) gratin dish.
-
13
Place one layer of potatoes side by side, slightly overlapping, on the bottom of the dish.
-
14
Spread a third of the onions over them and scatter a third of the bacon on top.
-
15
Arrange a second layer of potatoes, drizzle a 1/4 cup cream over it, and season with 1/4 teaspoon salt, a healthy pinch of pepper, and 1 teaspoon thyme.
-
16
Press the potatoes down with your fingers, letting the cream soak up through the layers.
-
17
This will ensure that the cream is evenly distributed and coats the potatoes well.
-
18
Arrange another layer of potatoes on top, followed by another third of the caramelized onions and the bacon.
-
19
Drizzle over another 1/4 cup cream, and continue with two more layers of potatoes.
-
20
Drizzle with 1/2 cup cream and season with 1/4 teaspoon salt and a pinch of pepper.
-
21
Press the potatoes down with your fingers again.
-
22
Scatter the rest of the onions and bacon over the potatoes, and drizzle with 1/3 cup cream.
-
23
Season one last time with 1/4 teaspoon salt, 1 teaspoon thyme, and a pinch of pepper.
-
24
The cream should cover the potatoes but not be soupy.
-
25
Add more cream if the gratin seems dry.
-
26
Cover tightly with aluminum foil.
-
27
Bake 1 1/2 hours, until the potatoes are tender when pierced.
-
28
Remove from the oven, and carefully uncover.
-
29
Turn the oven up to 425F and return the gratin to the oven.
-
30
Cook another 20 minutes or so, until the top is nice and golden brown (as in gratineed).
