Put a kettle of water on to boil. Put the onions into a saucepan, cover with the boiling water and cook over moderate heat for 5 minutes. Pour into a colander and put under cold running water. When the onions are cool enough to handle, drain well and peel .
Crush the rosemary as finely as possible, using a pestle and mortar or the end of a rolling pin.
Melt the butter gently in a large frying pan over moderate heat. Add the crushed rosemary, treacle or honey, Dijon mustard and soy sauce and mix well to form an emulsion.
Stir in the onions and cook gently, stirring and basting with the sauce, for 10–15 minutes, until the glaze has thickened and the onions are tender. Watch continuously to make sure the glaze does not burn.
Tip into a warmed serving bowl and garnish with the rosemary.
These onions make a sweet and spicy accompaniment to roasted and grilled red meats.