Bring a medium pan of water to the boil before adding 350g frozen butternut squash cubes

After 3-4 minutes, remove half of the butternut squash from the pan and allow to steam dry thoroughly

Leave the remaining squash cubes to cook for a further 2-3 minutes until you can easily insert a knife. When cooked, drain and leave to steam dry thoroughly

In a large pan over a medium heat, add ½ tbsp sunflower oil

Add 2 red onions, thickly sliced. Leave to cook for 7-8 minutes until softened stirring often so they don't gain too much colour

Add the squash pieces that you removed first to the pan with the onions along with 1 tsp sea salt, ⅛ tsp black pepper an ½ tsp dried sage

Cook for a further 5 minutes before setting aside to cool completely

Once the remaining squash cubes have thoroughly steamed dry, add back to the empty pan they were cooked in. Add 20g unsalted butter* 1 tsp sea salt, ⅛ tsp black pepper and ½ tsp dried sage and mash together. It doesn't have to be completely smooth, some texture is fine

Set the butternut squash aside to cool

Once the fillings have cooled, unroll a 320g sheet of ready rolled puff pastry

Cut the sheet of pastry into 4 by cutting it in half horizontally and vertically

Spoon the butternut squash mash in the middle of each of the four rectangles of pastry

Add 50g cooked and chopped chestnuts to the onion and squash mix. Stir to combine

Divide the squash mash between the four pastry rectangles making sure to keep a border round the outside of the pastry

Add the onion mixture on top of the mashed squash, again making sure to leave the border

Brush the outside of the pastry with beaten egg

Gather the pastry up to tuck around the filling. This doesn't have to be particularly neat as pastry is very forgiving

Preheat your oven to 180°C

Place the galettes on a baking tray - if you aren't confident of it's non stick abilities, line the tray with parchment paper

Cook for 20-25 minutes until the pastry is golden and crisp