Potato Gratin with Caramelized Onions

• cups whipping cream (I used 2%milk)↗2
• cloves garlic, slivered↗4
• peppercorns↗3
• sprigs fresh thyme↗2
• teaspoon salt↗3⁄4
• tablespoon vegetable oil↗1
• Spanish onions or 2 onions, finely sliced↗1
• large yukon gold potatoes, about 2 1/2 lbs↗3
• cup shredded gruyere cheese1⁄2

Step-by-step instructions

1. 1

   In saucepan, bring cream, garlic, peppercorns, thyme and salt to boil, reduce heat to low, cover and simmer for 15 minutes.

2. 2

   Remove from heat and set aside.

3. 3

   Meanwhile, in nonstick frypan, heat oil over medium low heat; cook onion, stirring often, until light brown, about 45 minutes.

4. 4

   Slice potatoes as thinly as possible, use mandoline if available.

5. 5

   Layer one quarter of the potatoes in greased 8 inch square glass baking or casserole dish; top with one third of the onion and one quarter of the cheese.

6. 6

   Repeat twice.

7. 7

   Top with remaining potatoes.

8. 8

   Strain cream mixture over potatoes, shaking casserole to distribute evenly; sprinkle with remaining cheese.

9. 9

   Bake at 300f degree oven until tender and knife inserted in bottom pierces potatoes easily, 1 1/2 to 2 hours.

10. 10

    (Make ahead: let cool; cover and refrigerate for up to 2 days. Reheat in 375f degree oven for 30 minutes.).