Champiñones Gratinados | Mushroom Gratin with Ham Mayonnaise

This simple recipe carries an explosion of flavour. It makes a great tapa or starterwhen you are entertaining friends or family as you can leave it hot in the oven until you need it.

 INGREDIENTS

• 4 portobello mushrooms, stalks trimmed

• 2 sprigs fresh thyme, leaves separated

• Olive oil

• The green part of 1 spring onion, finely chopped

• Sea salt and freshly ground black pepper
  
  For the ham mayonnaise:

• 1 egg yolk

• 1 garlic clove

• A pinch of salt

• 1tbsp lemon juice or vinegar

• 3 slices serrano ham, roughly chopped

• 150 ml mild olive oil

Preparation

1. Place the mushrooms on a roasting tray and sprinkle with sea salt, a bit of black pepper, the fresh thyme leaves and a drizzle of olive oil. Place in a cold oven and set the temperature to 180C/350F/gas mark 4. Bake for 15 minutes.
   

2. Meanwhile, for the ham mayonnaise, blend the egg yolk, garlic clove, salt, lemon juice and ham in a food processor and then start to add the oil in a steady stream until you have a mayonnaise. Otherwise follow the instructions on my video.
   

3. Remove the tray from the oven and sprinkle the mushrooms with the chopped spring onion. Top with a dollop of the ham mayonnaise and return to the oven for a good 5 minutes, or until the top has nicely browned.