French onion panade

Method

1. Put the oil in a heavy-based pan over a medium heat. Add the onions, half the butter and a pinch of salt. Cook until the onions begin to soften (about 5 minutes), then reduce the heat to low and cook, stirring regularly, for 45 minutes until the onions are very soft and sticky, and deeply caramelised. Add a drop of water if the pan looks dry.
2. Add the garlic and thyme and cook for 2 minutes more. Add the wine/vermouth/sherry, vinegar and sugar, then stir, scraping the any caramelised bits from the bottom of the pan. Turn the heat to high and bubble until the liquid has mostly evaporated. Remove from the heat and season with more salt, vinegar or sugar as needed. It should be sweet, sharp and deeply savoury.
3. Heat the oven to 160°C fan/ gas 4. Grease an oven dish (about 20cm x 30cm) with butter. Bring the stock to a simmer. Arrange half the bread in the base of the dish, tearing as needed to make a single layer, then evenly spread over the onion mixture. Sprinkle over half the cheeses and a grind of black pepper. Arrange the remaining bread on top, then ladle over spoonfuls of hot stock, allowing each to soak into the bread before adding more.
4. Dot the remaining butter over the bread, then scatter over the rest of the cheeses. Cover with foil and bake for 30 minutes. Remove the foil and return to the oven for another 15-20 minutes until bubbling and golden. Serve, scattered with more thyme and a green salad on the side.