Melt the butter in a saucepan and add the diced onion. Cook over a low heat for about 5 minutes until soft, but with no colour. Add the milk, the clove, bay leaf and thyme and place back on the heat. Heat the milk until just under boiling, remove and allow the flavourings to infuse for about ½ an hour.
Remove the herbs from the milk, and add the breadcrumbs and stir well.
Reheat, and if necessary add a little extra milk to achieve your desired consistency.
This can be made a few days in advance and kept in the fridge, or longer if frozen.