When the onion and garlic are cooked, it's time to add the diced Serrano ham. Sauté everything together for 2-3 minutes to release all of the flavour from the ham. It's important not to overcook it, as this could toughen the ham.
Next, add the peas to the pan. If you're using fresh peas, they may need a little more cooking (about 5-7 minutes), while frozen peas will cook in about 3-4 minutes. Stir well to infuse the peas with the flavours of the ham, onion and garlic.
If you want a juicier touch to your recipe, you can add a little vegetable stock (about 100 ml). This will give it an extra touch of flavour and help the peas cook more gently. Let the stock evaporate almost completely while the peas finish cooking.
Once the peas are tender and all the liquid has evaporated, remove the pan from the heat. Serve the peas and ham piping hot and, if you wish, you can sprinkle on some chopped fresh parsley for a touch of colour.