Shiitake Risotto

Ingredients

• 1500ml vegetable, chicken or mushroom stock
• 200g shiitake mushrooms
• 100g portobello mushrooms
• 2 tablespoons olive oil
• 1 medium onion, finely chopped
• 1 rib of celery (preferable from the centre), finely chopped
• 3 tablespoons butter
• 300g vialone nano or Arborio rice
• 125ml dry white wine such as pinot grigo
• A handful of finely chopped herbs such as parsley, chervil or tarragon
• 50g parmesan cheese, finely grated, plus extra to serve