Rosti-filled onions

• large onions↗4

  sliced into quarters, keeping root intact

• olive oil↗2 tbsp tbsp
• large potatoes↗2

  grated

• wholegrain mustard↗3 tbsp tbsp
• butter↗25g g
• vegetarian gruyère↗75g g

  -style cheese, grated

• large carrots↗2

  grated

Step-by-step instructions

1. 1

   Heat oven to 200°C (fan 180°C, gas 6). Place the onions on a baking tray, brush with olive oil, season, then bake for about 1 hour until golden and tender.

2. 2

   Meanwhile, mix the grated potato and carrot together, stir in the mustard and seasoning. Divide the mixture among the onions, then dot the top of each with a little butter.

3. 3

   Return the onions to the oven and bake for 15 minutes until meltingly tender. Sprinkle with the cheese and bake a further 5 minutes until the topping is golden and bubbling.