Put the yogurt in a bowl. In a small frying pan, heat the olive oil over a medium flame. Add the mustard and cumin seeds. When the seeds begin to pop, add the garlic and let it sizzle, without browning, about 10 seconds or so.
Scrape the contents of the pan into the yogurt. Stir in the ginger and chile. Season the sauce with salt and pepper. The sauce will keep in the fridge for a day o