Trim the roots off the fennel, taking only a thin slice, as the core will hold the pieces of fennel together in the pan. Cut the bulbs downwards into quarters. Halve the quarters carefully through the core, so that the pieces do not fall apart.
Heat the olive oil in a sauté pan over a gentle heat, and sauter the fennel for 10–15 minutes, turning the pieces carefully.
Add the stock, season lightly, add the thyme and cover the pan. Simmer for 10 minutes covered, until the fennel is just soft, then remove the lid and continue until the stock has evaporated – you will hear it start to sizzle – and the fennel is glazed and melting. Stop when it starts to brown.