Cook the entire quantity of Brussels sprouts in boiling salted water until just tender, rinse in cold water and drain well.
Mix the chicken with salt, pepper and paprika. Thread half of the Brussels sprouts and half of the chicken onto the skewers alternately. Heat the butter in a frying pan and grill the skewers on all sides.
Sauce: fry the shallot in butter. Add the second half of the Brussels sprouts, steam them, cover them with the stock and cook them until they are tender. Add the crème fraîche and purée. Mix with lemon zest, juice and herbs, season.
Divide the Brussels sprout sauce between the plates, add the skewers and the garnish.