Curried Potato Tart with Cilantro Yogurt

Crack open cardamom pods and remove black seeds; discard pods. Combine cardamom seeds and coriander seeds in spice mill or mortar and pestle and coarsely grind. Mix in a small saucepan with onion, garlic, jalapeño, butter, oil, mustard seeds, and curry powder. Season generously with salt and pepper. Cook over medium heat, stirring often, until simmering gently and onion is mostly softened, about 5 minutes. Holding back any solids, pour out ⅓ cup butter mixture and set aside for brushing phyllo. Set aside remaining butter mixture with spices for potato filling.

Preheat oven to 375°. Place potatoes in a large saucepan and add water to cover by at least 2"; season generously with salt. Bring to a boil, reduce heat, and simmer until potatoes are tender, 30–35 minutes. Let potatoes cool slightly, then cut into large pieces.

Toss potatoes, spinach, peas, cream, and ½ cup yogurt in a large bowl to combine. Mix in reserved spice butter with all the spices; season with salt and pepper.

Lay out a sheet of phyllo on a work surface and brush generously with some of reserved ⅓ cup spice butter (reheat if it has solidified). Transfer sheet to a large ovenproof skillet or shallow braising dish, letting any excess dough hang over the edges. Repeat with remaining sheets of phyllo, pressing each layer firmly into bottom of skillet. Top with potato filling and fold excess phyllo over filling to form a ruffly edge around the dish and leaving center exposed. Bake until phyllo is golden brown and crisp and filling is lightly browned, 35–45 minutes.

While tart is baking, purée garlic, cilantro, lime juice, and remaining 1 cup yogurt in a blender until smooth; season yogurt sauce with salt.

Cut tart into wedges and serve with yogurt sauce alongside.