Pop the onion in a pan with the milk,
cream, peppercorns and bay leaves.
Bring to a simmer, then turn off the heat
and leave to infuse for 30 mins. Pour the
milk through a sieve into a jug, then
return it to a cleaned pan.
Stir in the breadcrumbs, bring back to
the simmer and cook for a few mins (add
a splash more milk if you like your sauce
thinner). Stir in the butter, season with
salt, white pepper and nutmeg, then pour
into a warm serving jug or bowl. Or leave
to cool and chill or freeze for up to 1 month