Heat a large frying pan over medium heat, then add the speck and pan-fry, until golden. Remove the lardons to a plate and set aside.
Add the halved cos lettuce and pickling onions, cut-side down and fry until well-browned and slightly blackened.
Add the peas and wine and bring to a simmer.
Add the butter, cover and simmer for about 15-20 minutes, or until the onions are tender and the sauce is reduced to a coating consistency.
Toss the lardons back through the pan, transfer to a serving dish and serve.
