Heat the oil in a saucepan. Add the onion
and gently cook over a medium heat for 5-6
mins until softened but not coloured. Add the
garlic and cook for a further min. Stir in
three-quarters of the petit pois, then pour in the
stock. Bring to the boil and simmer for 10-12
mins. Meanwhile, grill the bacon until crisp.
Allow to cool for a few mins, then carefully
transfer to a food processor and whizz until
smooth. You might need to do this in two
batches, depending on the size of your
Return the soup to the pan and add the
remaining petit pois. Bring to the boil and
simmer for 2 mins or until the whole peas
are tender. Season to taste, then stir in the
butter, if using. Break the bacon into pieces
and scatter over bowls or mugs of soup.
The soup can be made up to a day ahead;
just grill the bacon on the day.