When the oil is at frying temperature, dip an asparagus spear into the flour, then the egg mixture to coat, then roll it in the breadcrumbs. Repeat with a few more spears. Immediately lower the asparagus carefully into the hot oil and fry for a few minutes until golden brown all over. Remove the spears carefully using a slotted spoon or metal tongs and transfer to the plate to drain. Repeat with the remaining spears but do not overcrowd the pan – fry in small batches. Serve hot, sprinkled with salt flakes and with the saffron yogurt on the side for dipping.