Toast the bread until dark brown, then leave to cool. Blitz in a food processor to rough crumbs.
Heat half the oil in a saucepan and cook the onion for 10 mins until just brown and sticky. Add the bay, thyme and milk, then season with the spices and salt and pepper. Bring to the boil and simmer for 5 mins.
Remove the herbs, then stir in all but a handful of the breadcrumbs. Cook over a low heat until thick. If you like, blitz until smooth. Will keep, chilled, for two days.
Meanwhile, fry the rest of the crumbs in the remaining oil until golden.
Add the cream to the sauce and heat through, then tip into a dish and spoon over the fried crumbs and a drizzle more oil. Will keep, covered, in the fridge for up to two days.