Preheat oven to 200.c
Set aside 1/2 of the shallots and put the rest in a small saucepan with 2 Tbsp. of the oil and the garlic. Cook over medium-low heat until the shallots are soft and start to go translucent not browned, about 5 minutes. Add the peas and the water and season with a pinch of salt and pepper. Bring to a simmer over medium-high heat and then reduce the heat to medium low. Cover the pan and cook until the peas are tender.
Transfer the contents of the pan to a blender and purée to a smooth consistency, adding a little water if needed. Season to taste with salt and pepper. Return the purée to the saucepan, cover, and set aside to keep warm before serving
Chop the pancetta into 1cm pieces and place on a baking sheet and bake until golden brown and crisp
In a small bowl combine the parsley, lemon zest, garlic and shallots and set aside.
Pat the scallops dry and season them generously with salt and pepper. Heat the butter and the remaining 1 Tbs. oil in a Large frying pan on a high until very hot turn the heat down to medium and add the scallops and cook, flipping once, until golden brown on both sides and almost firm to the touch, 2 to 4 minutes per side. Transfer to a plate.
Portion the warm pea purée among four large salad plates or between two dinner plates. Arrange the scallops on the purée and sprinkle the pancetta around the plate. Sprinkle the Gremolata over all and finish with a generous drizzle of olive oil