Place the currants into a small bowl and squeeze the orange juice into currants. Allow to rest and soak up the juice whilst you prepare the rest of the recipe.
Whisk together the homemade flour blend, almond flour and salt in a medium sized mixing bowl until well combined. Set aside for a moment.
Place the butter and sugar in a large mixing bowl and cream together for about two minutes until light and creamy.
Add the flour mixture and vanilla and bring into a smooth dough. You can start by combining the ingredients in the mixing bowl and then tipping it out on to a work surface to finish bringing together.
Split the dough in half and shape each half into a thick rectangle. Wrap the dough in cling film (plastic wrap) or baking parchment and place in the fridge for 20-30 minutes to firm up a little.
Place each dough half onto large pieces of baking parchment. Roll each rectangle out, one at a time, using a rolling pin, into long thin rectangles, 38cm (15 inches) long and 15cm (6 inches) wide. If the dough breaks apart slightly as you are rolling out just press back together or patch up any large tears with dough from the edges.
Drain the currants to remove any excess orange juice then tip them out along the centre of one of the pieces of dough.
Spread our the currants to the edges.
Lift the other piece of dough carefully using the baking parchment and place on top of the currant layer. Press these layers together then use a rolling pin to firmly press them together.
Neaten up the edges of the biscuit dough then slice the dough, 4 cuts widthways, 3 cuts lengthways to make 15 rectangular biscuits.
Divide the biscuits between two baking trays (I used 40cm (15”) x 28cm (10”) sized baking trays) lined with baking parchment. Placing the biscuits spaced well apart.
Fork tine the top.
Place the baking trays full of biscuit dough in the fridge and chill for 15 minutes.
Meanwhile pre-heat the oven to 190°C / 170°C fan assisted / gas mark 5 / 375°F.
Finally scatter over extra caster sugar across the biscuits then place in the oven and bake for 12 - 15 minutes until just turning lightly golden.
Remove from the oven and allow the biscuits to fully cool and firm up on the baking trays before enjoying.