Melt the butter in a pan. Stir in the plain flour and cook for 2 mins. Add some warmed milk to the butter and flour mixture and whisk in well. Gradually add the rest of the milk. Bring up to the boil, whisking continuously. Whisk in the egg yolks and bring back to the boil before adding the Tracklements Beer Mustard, Worcester sauce and ale. Then whisk in the Cheddar cheese until smooth.
Toast the bread on both sides. Spread the rarebit evenly over the surface and place back under the grill until golden brown on top.
Serve with pint of ale.