In a small pan, soften the white parts
of the spring onion in the butter, then stir
in the flour for 1 min. Very gradually, stir in
the beer to make a thick sauce (like when
making a white sauce). Take off the heat
and stir in green parts of the spring onion,
the egg, breadcrumbs and cheddar.
Season and chill until you’re ready to use.
Lightly toast crumpets, and heat grill to
high. Arrange crumpets on a baking sheet,
pile rarebit mixture on top and grill for a
few mins until piping hot and golden brown.