Preheat your oven to 170 Fan / 190 C / 375 F and line a couple of large trays with parchment or silicon mats
If you're planning ahead, you'll want to leave the butter out overnight or at least for a few hours to soften. Alternatively soften the butter in a microwave. Make sure to soften only, not melt!
Put the butter in the bowl of a stand mixer with a paddle attachment and beat until pale
Add the icing sugar and beat together with the butter until creamy and fluffy. Scrape down the sides of the bowl once or twice to make sure everything is mixing well
Add the butter flavouring, flour, cornflour and vanilla and beat just until the mixture forms a sticky dough
If the mixture is too stiff to pipe beat in a few drops of boiling water
Transfer the dough to a piping bag and pipe shapes until you've used all the dough. If it helps, draw in pencil on the underside of the parchment as a guide while piping
Chill the trays in the fridge for at least 30 minutes
Sprinkle the granulated sugar over the cookies then bake for 20 minutes until golden - they will firm up a little on cooling
Store in an airtight container
Recipe by The Cook & Him at https://thecookandhim.com/recipes/vegan-danish-butter-cookies/