Heat the milk with the peppercorns and bay leaves very gently until it starts to simmer.
Strain the milk into a jug and keep warm.
Put a saucepan over a gentle heat – add the butter and melt it slowly – it should not turn brown.
As the butter melts add the flour in small amounts and stir to make a smooth paste. That is your roux.
Add the warm milk a little at a time, keeping the heat low, and stir vigorously until all the milk has been mixed into the roux in small steps, a little bit at a time. You are aiming for a smooth sauce. When you have mixed in about half the milk, use a hand whisk to add the rest, and keep up a quick pace.
Turn the heat down to the lowest setting and cook for about 5 minutes – whisking it periodically.
Add seasoning.
Keep the sauce warm by putting taking it off the heat and covering the pan with cling film.
Recipe by JAQUO Lifestyle Magazine at https://jaquo.com/authentic-lasagne/