Line the baking sheets with baking paper.
Sift the flour into the bowl of the food processor, add the butter and process until a breadcrumb consistency has been reached (about a minute).
Add the sugar and egg yolks and process until a dough ball forms.
Remove one-third of the dough, add vanilla to what’s left and pulse to incorporate it.
Wrap this dough in clingfilm and place in the fridge until an hour before you make the biscuits at which point remove from the fridge and allow to come to room temperature.
Put the reserved dough back in the processor with the rosewater and a drop of food colouring.
Pulse and add more colouring to achieve an intense colour. If the dough has become too soft, pulse in a few spoonsful more flour until it reaches a similar consistency to the vanilla dough.
Thickly roll out the coloured dough between baking paper.
Use a small 3-4cm heart cutter to stamp out hearts.
Keep re-rolling and stamping until all the dough is used.
Line up hearts on top of each other and press to form a cylinder, taking care to retain the heart shape.
Wrap in clingfilm and freeze for 3 hours until solid.
When the heart dough is hard, use your hands to roll the vanilla dough into 3 logs the length of the heart stack.
Stick one to each ‘side’ of the heart tube, pat together to form a fat log, then gently roll on your work surface until you have a smooth, perfectly round surface.
Wrap in clingfilm and chill for 2 hours.
Preheat the oven to 180C/350F/gas 4.
Use a sharp serrated knife to slice the log into 1cm-thick discs. You may need to press the edges a little to get circular discs.
Place on the lined baking sheets, allowing space for spreading.
Place in the preheated oven and bake for 20 minutes.
Remove from the oven and allow to cool on the baking sheets for 10 minutes before transferring to the cooling rack. Allow to cool to room temperature before serving or storing. The biscuits will keep for up to 4 days in an airtight container.
