In a solid pan melt the butter down with the olive oil, slice the onions and sweat down gently for 10 minutes.
Turn up the heat a bit, and stir in the sugar, this will help to caramelise the onions. Watch them and cook for about 20 minutes. We want the onions to be lovely sweet and golden, not burnt.
Add the sliced garlic, rosemary, mustard powder and the flour and cook through for two minutes, stirring constantly.
Add the white wine and bring to a simmer for a couple of minutes.
Add the stock and stir well, simmer for 30 minutes until thick and lovely. Check seasoning, loads of black pepper is great with this.
Put the slices of French bread under the grill and load up with the grated cheese, toast to perfection.
Serve the soup, and to with a Gruyere crouton. A taste of heaven.
FOR THE SAVOURY BUNS
To make the bread dough, put the flour, yeast, salt and sugar or honey in a bowl and drizzle in the olive oil, then the water, mixing together until it forms together in a dough.
Add the ham, cheese and chives. Knead in the bowl for a minute until the additions have worked in a little, then knead on a floured surface until the dough is smooth.
Return to the bowl, cover with a damp cloth or cling film and leave to rest somewhere warm for 1.5-2 hours, until doubled in size.
Preheat your oven to its highest setting. Knock back the risen dough and divide into 8-10 even pieces. Knead and shape into balls, then place in a large cake tin or a small roasting tin, which has been lined with greaseproof paper.
Cover with a damp towel again and leave to rise for another 20-30 minutes until risen and squashing together.
Brush lightly with the egg glaze (you need a very light touch if the bread dough is at all puffy/springy, but still best done at this stage), then sprinkle over the remaining cheese.
Bake in the oven for 20-25 minutes until cooked through and a golden brown. They should feel slightly hollow. Lovely served warm from the oven or cold – but warmed through best.