Whiz the bread slices in a blender into fine breadcrumbs. Heat a knob of butter in a small skillet, add the shallots and cook on low heat until translucent and softened. At the end of cooking add the garlic and stir in. Place all the ingredients apart from the pancetta slices reserved for wrapping in a large bowl and mix thoroughly, best using your hands. Turn out onto a wooden board, wet your hands and form a tight loaf.