If you can find Crawford's biscuits in Ireland, they still do an arrowroot biscuit, because I occasionally buy a packet!
Here's Mrs Beeton's arrowroot biscuit recipe, as revised by the Foody site
MRS BEETON'S RECEIPT
Arrowroot biscuits or Drops
1738. INGREDIENTS - 1/2 lb. of butter, 6 eggs, 1/2 lb. of flour, 6 oz. of arrowroot, 1/2 lb. of pounded loaf sugar.
Mode - Beat the butter to a cream; whisk the eggs to a strong froth, add them to the butter, stir in the flour a little at a time, and beat the mixture well. Break down all the lumps from the arrowroot, and add that with the sugar to the other ingredients. Mix all well together, drop the dough on a buttered tin, in pieces the size of a shilling, and bake the biscuits about 1/4 hour in a slow oven.
Sufficient to make from 3 to 4 dozen biscuits.
MODERN225g (8oz) Butter
225g (8oz) Flour
225g (8oz) Caster Sugar
170g (6oz) Arrowroot
6 Eggs
Beat the butter to a cream.
Whisk the eggs to a strong froth.
Add them to the butter, stir in the flour a little at a time and beat the mixture well.
Break down all the lumps from the arrowroot and add it with the sugar to the other ingredients.
Mix all well together, drop the dough on a buttered tin, in pieces the size of a shilling.
Bake the biscuits about 15 minutes in a slow oven. Time: 15 minutes.
Sufficient to make from 3 to 4 dozen biscuits.