Heat 1/4 cup olive oil in a large skillet over medium. Cook coriander seeds and cardamom, stirring constantly, until starting to brown, about 2 minutes. Add onion and cook, stirring occasionally, until translucent and slightly browned, about 5 minutes. Mix in garlic and ginger and cook, stirring, 1 minute. Add spinach by the handful, letting it wilt slightly after each addition before adding more. Cook until all of the spinach is just wilted, about 3 minutes. Remove pan from heat and add serrano and lime juice; season with salt. Let cool 5 minutes. Stir in 1/2 cup water, then gently fold in paneer. Cook until the paneer is slightly softened and has absorbed some of the sauce, about 5–7 minutes.