Cut the butternut squash in half and peel off the skin. Add the squash to a lidded pan with the thyme and vegetable stock. Season generously and cover. Bring to a simmer over medium heat and cook for 15-20 minutes, until the squash is tender. Drain and let it cool.

In a food processor, blend the mushrooms and garlic until finely chopped. Heat 2 tablespoons of olive oil in a pan, add the mushroom mixture, and cook until it becomes dry. Season with salt and pepper, stir in the pumpkin seeds (or crushed walnuts), and let it cool.

In another pan, heat 1 tablespoon of olive oil. Add the chopped onion, cranberries, and grated garlic; sweat for about 3 minutes. Stir in the plain flour and cook for another minute. Then add the red wine and reserved squash stock, letting it simmer for 10 minutes until thickened.

Preheat your oven to 200°C (180°C fan/gas mark 6). Cut the puff pastry into 4 rectangles. Place 2 rectangles on a baking tray and top with half of the mushroom mixture, followed by the cooled squash. Press the remaining mushroom mixture around the squash.

Brush the exposed pastry edges with the beaten egg, then cover with the remaining pastry rectangles. Seal the edges by pressing down. Brush the tops with egg wash and bake for 35-40 minutes until golden brown.

Slice the Butternut Wellington and serve it with the rich cranberry gravy and your favorite seasonal vegetables.