4 large Spanish onions (about 900g/2lb)
3 tbsp extra virgin rapeseed oil
4 thyme sprigs
2 bay leaves
1 rounded tbsp plain flour
1 tbsp Swiss vegetable bouillon
For The Topping
1 garlic clove , crushed
1 tbsp extra virgin rapeseed oil
4 long slices from a baguette
25g Parmesan , coarsely grated
50g Gruyère , coarsely grated
leaves, then season with a little salt. It will seem like a lot of onions, but they reduce right down. Cook over a high heat for 5 min, stirring often. The onions shouldn't brown yet, just start to soften. Lower the heat, then cook slowly for 35 min, uncovered, stirring often until the onions have reduced right down and are very soft.
While the onions are cooking, bring the water to a boil in a small pan, then bubble away for 30 secs. Remove and leave to cool. Tip the flour into a small heavy pan and toast over a medium heat for a few min, stirring occasionally, until light brown in color. Set aside.
When the onions are very soft and reduced, turn up the heat so they caramelize, then cook for another 12-15 min, stirring along the bottom of the pan occasionally to mix in the brown sticky bits. When the bottom of the pan and all the onions are sticky and a rich brown color, stir in the flour. With the heat still high, gradually pour in the water, again stirring in the bits from the bottom. Pour in 1.2 liters of cold water. Stir in the bouillon, then slowly bring everything to the boil. Skim off any froth from the surface. Simmer for 15 min so all the flavors can mingle.While the soup simmers, make the topping. Heat oven to 200C/fan 180C/gas 6. Mix the garlic and the oil together. Brush all over the bread slices, then cut each one into cubes. Scatter over a baking sheet, then bake for 8-10 min until golden. Set aside. Line a baking sheet with baking parchment or a sheet of non-stick silicone. Remove the leaves from the remaining thyme sprig, then mix with the grated Parmesan. Scatter and spread over the lined baking sheet into a 13 x 8cm rectangle. Bake for about 8 min until melted and turning golden. Remove, leave to firm up, then snap into jagged pieces.