CHEESY POTATO AND KALE GRATIN WITH RYE CROUTONS

Steps:

• Arrange a rack in center of oven; preheat to 350ºF. Arrange bread slices on a rimmed baking sheet and bake, flipping once halfway through, until dry and lightly toasted, 15-20 minutes. Let cool. Transfer to a resealable plastic bag and break into irregular, 1/2"-1" pieces. Transfer to a medium bowl; set aside.
• Meanwhile, wash and spin-dry kale, then layer between paper towels or a large clean kitchen towel and pat dry.
• Mix Gruyère and Parmesan in a medium bowl. Shingle one-quarter of potatoes in 3 or 4 rows, slightly overlapping, in bottom of baking dish. Sprinkle with one-quarter of thyme, 1/4 tsp. salt, and 1/8 tsp. pepper. Top with 2 cups kale and one-quarter of cheese mixture. Repeat 2 more times. Shingle remaining potatoes over cheese; top with 1/4 tsp. salt, 1/8 tsp. pepper, and remaining thyme. Reserve remaining kale and cheese.
• Stir cream, garlic, 1/4 tsp. salt, and 1/8 tsp. pepper in a liquid measuring cup. Pour evenly over potatoes.
• Bake gratin 40 minutes. Cover with foil and continue to bake until cream is bubbling and thick and potatoes are tender when pierced with a paring knife, 35-45 minutes more.
• Meanwhile, toss reserved croutons with 2 Tbsp. oil in a medium bowl. Toss remaining kale with remaining 1 Tbsp. oil. Top gratin with kale, remaining cheese, then croutons, allowing kale pieces to peek through. Bake gratin until croutons are golden brown and exposed kale edges are well-crisped, about 15 minutes more. Let cool at least 10 minutes before serving.
• Do Ahead
• Bread can be toasted 3 days ahead. Store in an airtight container at room temperature. Kale can be torn, washed, and patted dry 3 days ahead. Wrap in paper towels, place in a resealable plastic bag, and chill.
• Gratin can be made 1 day ahead. Let cool, then wrap tightly in plastic and chill. Bring to room temperature, cover with foil, and warm in a 300ºF oven until heated through, 15-20 minutes. Uncover and continue to warm to re-crisp croutons and exposed kale edges, about 5 minutes.