Melt 2 tablespoons (25 g) of the butter in a shallow pan large enough to take the fillets of brill side by side. Add the shallots, sugar, and garlic, and cook until lightly browned. Barely cover with some of the chicken stock, and add the ham, 1/4 teaspoon salt, and some pepper. Simmer gently until both the shallots and garlic are tender. Then turn up the heat and boil rapidly until the stock has reduced to a thick, sticky glaze, shaking the pan now and then so that the onions and garlic become well coated. Remove them from the pan to a plate and keep warm. Set the pan to one side, unwashed.