Preheat the oven to gas 7, 220°C, fan 200°C. Toss the butternut squash in 2 tablespoons of oil, put in a deep-sided baking tray or roasting tin and bake for 10 minutes. Add the bacon, cut into 2·5cm (1in) pieces, and bake for a further 10 minutes. Meanwhile, in a blender, whizz the flour, egg, milk and a pinch of salt into a double cream-like batter. Stir in the thyme. When the bacon's ready, pour the batter evenly over the bacon and squash. Bake for 30-40 minutes, until golden and puffed. Heat the remaining oil in a frying pan. Add the onions and gently cook until soft (about 15-20 minutes). Add the sugar and cook until dissolved. Stir in 1 tablespoon of flour. Pour over the stock, bring to the boil, simmer for 5 minutes until thickened. Cut into wedges; serve with the gravy.
