Pierce the casings of the bockwurst and arrange the sausages in a medium-size skillet. Add 1 inch of water, bring it to a simmer over medium heat. Keep simmering until the water completely evaporates, about 10 minutes. Add EVOO and continue to cook to let the skin crisp up.
Add the butter and shallots to a medium-size saucepot over medium-high heat. Saut until soft and translucent. Add the flour and cook for about 2 minutes, then add stock and bring to a boil. Reduce the stock until it thickens, then add the cream, nutmeg and mustard. Cook for 2 minutes more and season with salt and pepper. Turn the heat off, and cover to keep the sauce warm while you prepare the broccolini.
Trim and discard the bottom half-inch from the broccolini stems then cut into one-inch pieces. Steam broccolini, covered, in small skillet with half an inch of boiling water for 3 minutes. Drain and, just before serving, hit it with a squeeze of a half a lemon.
In a medium saucepan, cover the peeled and quartered potatoes with water. Bring to a boil and cook potatoes 10 minutes, until fork tender. Turn the heat off, drain potatoes then return them to the hot saucepan on the stovetop to dry the potatoes out. Add about 3/4 of the creamy mustard sauce to the potatoes, and smash to desired consistency. Season potatoes with salt and pepper to taste and stir in chopped herbs.
Place a generous portion of the creamy mustard smash onto plate and place a bockwurst on top. Top with a large spoonful of the reserved creamy mustard sauce and serve the steamed broccolini alongside.