Rustic Potato Pie

Ingredients

• 4 tablespoons (1/2 stick) unsalted butter, melted, divided, plus more for pan
• 2 tablespoons rendered bacon fat, melted
• 1 teaspoon (or more) kosher salt
• 1/2 teaspoon freshly ground black pepper
• 2 pounds medium Yukon Gold potatoes, unpeeled, cut into 1/8"-thick slices with a mandoline or V-slicer
• 1 small sweet onion, very thinly sliced

Instructions

1. Arrange a rack in middle of oven; preheat to 425°. Brush parchment-lined baking sheet with butter.
2. Melt bacon fat in a large bowl and add 2 Tbsp. butter, 1 tsp. salt, and pepper. Add potatoes; toss to coat.
3. Arrange 1/4 of potatoes in an even layer in a circle on baking sheet, overlapping as needed.
4. Toss onion in a large bowl with 1 Tbsp. melted butter.
5. Arrange 1/3 of onion over potatoes.
6. Repeat layers twice more, finishing with a layer of potatoes.
7. Bake until potatoes are tender, about 45 minutes. Brush with 1 Tbsp. butter. Bake until edges of potatoes are deep golden and top is crisp, 5–10 minutes longer.
8. Run a thin spatula under potatoes to loosen from parchment paper.
9. Slide onto a platter. Season with salt, if desired.