2/3 cup icing sugar
2 teaspoon vanilla essence
2 cups plain flour
1/3 cup custard powder
To make yoyo lemon filling:
1 cup icing sugar
2 teaspoons lemon juice
(Optional - yellow food colouring to give an extra bright yellow colour to the filling!)
Preheat the oven to 140 degrees celsius and prepare a baking tray by lining it with silver foil or lightly greasing it with butter or canola spray.
Use an electric mixer to cream the butter, icing sugar and vanilla together until fluffy and glossy. This should take about 1-2 minutes.
In a separate bowl, combine the flour and custard powder. Sift these into the sugar, butter and vanilla mix.
Use a wooden spoon to fold the flour into the butter and icing sugar mix until the ingredients are about half way combined. Then jump back onto the electric mixer and beat the ingredients together the rest of the way. Folding the flour and custard powder in half way will prevent a cloud of dust billowing out when you switch back to the electric mixer!
Place some flour in your hands and roll balls of the prepared biscuit dough. Put these on the baking tray with about 2 centimetres of space between each biscuit to allow for flattening and spreading.
Dunk a fork into some flour and shake of the excess to coat the fork so that it doesn't stick to the dough. Lightly press down on the tops of each biscuit dough ball with the fork to leave a fork impression and slightly flatten out each biscuit. Coat the fork in additional flour if it begins to stick to the biscuit dough.
Bake for 15-20 minutes, or until cooked. Test by bringing one of the biscuits from the oven and breaking it open. If the centre is still gooey and a darker colour to the outer layers, leave the biscuits in the oven for another 2-3 minutes, then test again.
Once cooked, bring the biscuits out of the oven and cool on a wire rack.
To fill and construct:
Combine the butter, icing sugar, and lemon juice (plus food colouring if using) and mix either with a spoon of an electric mixer.
Place a layer of the lemon filling on the flat side of one of the cooked biscuits, then join to the flat side of a second biscuit. Allow the filling to set (for at least 5-10 minutes). Store completely constructed lemon yoyos in an airtight contained, or store the biscuits and make the lemon filling fresh later.