Preheat the oven to 180C/350F/Gas 4. Lightly grease two baking trays lined with baking parchment.
Measure the butter and sugar into a bowl and beat together until light and fluffy. Beat in the egg yolk. Sieve in the flour and spices and add enough milk to give a fairly soft dough. Bring together, using your hands, to make a soft dough.
Halve the mixture and set half to one side.
For the traditional currant biscuits, add the currants to the remaining half of the mixture and knead it lightly on a lightly floured work surface. Roll out to a thickness of about 5mm/¼in. Cut into rounds using a circular cutter. Place on the prepared baking trays. Sprinkle with caster sugar.
Bake in the preheated oven for 15 minutes, or until pale golden-brown. Keep a careful eye on the biscuits - it doesn’t matter if you open the oven door to check. Sprinkle with caster sugar and lift onto a wire rack to cool. Store in an airtight container.
For the iced biscuits, knead the remaining half of the biscuit dough mixture lightly on a lightly floured work surface. Roll out to a thickness of 5mm/¼in. Cut out Easter biscuits using an assortment of shaped cutters, such as bunnies, Easter eggs, chicks, spring flowers.
Lightly grease two baking trays lined with baking parchment.
Place the biscuit shapes on the prepared baking trays and bake in the preheated oven for 10-15 minutes. Remove from the oven and lift on to a wire rack to cool.
To make the icing, pass one teaspoon of lemon juice through a fine sieve, to remove any pips or bits. Mix the icing sugar with the lemon juice, and then add about two tablespoons of water, adding it little by little until you have a relatively stiff but smooth icing. Add a splash more sieved lemon juice if necessary.
Divide the icing into separate bowls and mix in food colourings of your choice into the separate bowls of icing, until you achieve the desired shade.
Spoon a little icing into a piping bag and pipe your decorations onto the biscuits. For a smooth finish, you can pipe the outline of your design in the firmer icing, then slacken it down a bit by mixing in a little more water, giving the icing more of a runny consistency, and use this to fill in the designs.