Crispy Potato-Leek Kugel

Preheat oven to 375°. Cut 4 potatoes into 1" chunks and place in a medium pot. Cover with cold water by 1". Season water generously with salt, bring to a boil over medium-high heat, and cook until potatoes are tender, 10-12 minutes. Drain well, transfer to a large bowl, and mash with a potato masher; set aside.

Meanwhile, heat 2 Tbsp. oil in a large skillet over medium until shimmering. Add leeks, 1/4 tsp. salt, and 1/4 tsp. pepper and cook, stirring frequently, until softened and golden, 5-8 minutes. Add garlic and cook until fragrant, 1-2 minutes more. Remove pan from heat and let cool slightly.

Grease bottom and sides of an 8x8" baking pan with 2 Tbsp. oil. Place pan in oven for 10 minutes.

Meanwhile, grate 3 potatoes and onion using the large holes of a box grater or a food processor fit with a shredding blade. Wrap potatoes and onion in a clean dishtowel or several layers of paper towels and squeeze out as much liquid as you can; add to the bowl with the mashed potatoes. Stir in sautéed leeks and garlic, eggs, 2 Tbsp. oil, 1 Tbsp. thyme, 2 tsp. salt, and 1/4 tsp. pepper; mix until well combined.

Thinly slice remaining 2 potatoes and toss with remaining 1 Tbsp. oil, 1 tsp. thyme, 1/4 tsp. salt, and 1/4 tsp. pepper in a medium bowl; set aside.

Carefully remove preheated pan from oven and transfer potato-onion mixture to the pan (it should sizzle when it hits the hot oil). Smooth top with a spatula. Layer potato slices over the top in a shingled fashion. Bake until golden brown and cooked through, 60-75 minutes. Heat broiler; broil kugel until crispy crust forms, 1-2 minutes, watching carefully so it does not burn. Let cool briefly, then cut into squares to serve.