Boil the potato for 15 mins until soft.
Meanwhile, place 25g of the butter and all
of the cream in a heavy-based pan and bring
to the boil. Slice the spring onions, separating
the green and white parts, then add the
white slices to the boiling liquid and cook for
1-2 mins to soften. Pass the cooked potato
through a ricer or sieve to a really fine mash,
then add to the pan and mix everything
together. Set aside to cool.
Add the crabmeat and sliced green bits of
spring onion to the potato mixture and stir
together. Melt the remaining butter. Unwrap
the filo pastry and cover with a clean, damp
tea towel to prevent it drying out. Brush
melted butter over one sheet, place another
on top and brush again with butter. Then
add a final sheet of filo.
Cut the filo sheets lengthways into 3 long
strips. Then cut each strip in half across the
middle. Place a teaspoon of the crab onto
the bottom right-hand corner of each filo
strip. Fold the filo over to make a triangle,
then fold again, rolling up the strip. When
the mixture is enclosed and you have a neat
triangle shape, place on a baking sheet and
brush with more butter. Can be made ahead
up to this point and frozen for up to 1 month.
Heat oven to 200C/fan 180C/gas 6. Cook
the rolls for 15-20 mins until golden and
crisp. To serve, pile the parcels up on a plate
or bowl, then scatter over with extra sliced
spring onion, if you like.