Heat some olive-oil in a large fry pan over low heat. Add the onions and a good pinch of sea salt and cook very slowly for 15-20 minutes, stirring occasionally to prevent them from catching. Don’t be tempted to turn the heat up, as you don’t want the onions to burn. Add some black pepper corns and green, some tarragon leaves and cook for another 5 minutes.
Let them cool at room temperature and store them in airtight container and use when required.
If using a frying pan or griddle pan, put it on a high heat and let it get really hot. However you decide to cook your burgers, they’ll want around 3 or 4 minutes per side – you may have to cook them in batches if your pan isn’t big enough. When your burgers are nearly cooked on one side, add the rashers of coppa di Parma – whichever way you’re cooking them – then flip the burgers and cook the coppa di Parma until golden and crisp. When the burgers are cooked to your liking and it’s all looking really good, halve your burger buns and warm them through. Put the coppa di Parma on a plate lined with kitchen paper to drain. Add the toffee cheddar cheese on the burger until melted. (you can use the oven for this is more quicker and easier).
Wash potatoes thoroughly. Place potatoes in boiling water for 5 minutes or until partially tender. Drain and set aside in a bowl of cold water for at least 2 minutes to cool down. Slice each potato in half. Do not peel. Add olive oil in a preheated pan. Place potatoes in cut side down with the ½ lime. Season with sea salt and green pepper. Fry over medium heat for at least 4 minutes or until the cut side starts to brown. Add more olive oil if the pan starts to dry out. Once potatoes start to brown, add the butter, honey fresh lemon thyme and tarragon leaves, flip over and allow to brown for few minutes. Stir continuously over medium-low heat until the potatoes are golden brown.
Cut the cherry tomatoes in half, cut the Chinese lettuce with your hand in uneven pieces dress them with some olive oil, sea salt and black pepper.
When everything comes together pop your burgers on to their buns, add all your lovely toppings and your caramelized onions, then place the salad and the sauté potatoes on the plate and served.