For the casserole; heat 1 tablespoon of the oil in a flameproof casserole dish, add the shallots and sausages and cook for 8-10 minutes over a moderate heat, stirring occasionally until lightly golden.
Add the bacon, 2 garlic cloves and mushrooms and cook for a further 3-4 minutes.
Add the stock, wine, mustard, most of the thyme, the blended cornstarch and season to taste. Bring to the boil and simmer gently for 20-25 minutes, stirring occasionally.
For the croutons, heat the remaining oil in a frying pan, add the remaining crushed garlic and bread triangles and fry for 1-2 minutes each side, until crisp and golden. Drain on kitchen paper.
Serve the bourguignon sprinkled with the remaining chopped thyme, and the croutons arranged around the edge.