In a small bowl, place the water and the 1tbsp granulated sugar. Sprinkle the yeast over the surface of the water and leave to stand for 5 minutes.
In the bowl of a stand mixer fitted with the dough hook attachment, place the remaining sugar, flours and salt. Mix briefly to combine. Create a well in the centre of the flour, add the water and yeast mixture along with the 100g of room temperature vegan butter. Knead to combine on a medium speed and leave running for around 8 minutes. A nice ball of dough should form.
Lightly grease a medium bowl and transfer the ball of dough into it. Cover with cling film or a damp tea towel and leave to prove for an hour or until it has doubled in size.
Once proved, turn the dough out onto a work surface (you don’t need to dust the surface with flour, the dough shouldn’t stick too much). Using your fingertips, push out any air bubbles from the dough. Fold the dough into a tight oblong and flatten with the palm of your hand. Place on a baking sheet and place in the freezer for 30 minutes. After 30 minutes flip the dough and return to the freezer.
While your dough is freezing, make the “slab” of butter for the lamination process. Take a large sheet of greaseproof paper and fold the edges over to make a square roughly 20cm x 20cm. Unfold and then place the remaining 250g vegan butter into the centre of the parchment. Fold the parchment back over the butter and roll out with a rolling pin until the butter is an even layered 20x20cm square. Place in the fridge to chill for minimum 30 minutes.
Once chilled, remove the butter from the fridge. Once your dough is quite firm in the freezer, remove it and roll it into a roughly 20x40cm rectangle. If you like, you can trim the edges to make it exact, but it’s not essential. It’s very important that you do not handle the dough too much - the heat of your hands will melt the butter, so keep everything as cold as possible and keep your hands off the dough!
You should now have a rectangle of dough which is twice the size of your butter. Place the butter on one half of the dough and fold the dough over. Using a rolling pin, flatten the dough to seal the butter in between the two layers. Roll the rough into a long 20x70cm rectangle and the fold in thirds (as in this video, around the 4.15 mark). Wrap the pastry in cling film and then place in the fridge to chill for 30 minutes.
Remove the chilled dough from the fridge and roll out again into a 20x70cm rectangle. Fold into four layers (as in this video), wrap the rectangle of dough in cling film again and place in the fridge for another 30 minutes.