Cut the sweet potato into cubes of +/- 1 cm and the red onions into quarters. Halve the sweet peppers and cut into 1 cm wide strips. Place the vegetables with the garlic cloves on a baking tray and cover with olive oil and thyme. Season generously with salt and pepper.
Slide the baking tray into the preheated oven and grill for 30 minutes until cooked.
Push the garlic cloves out of the peel and mix together with the vegetables and chicken stock to make a smooth soup. Season with salt and pepper.
Cover 2 slices of bread with chicken white and Brugge Mature and cover with the other slices of bread. Spread butter on the outside and fry in a frying pan until golden brown on both sides. Cut off the crusts and cut the sandwiches into strips.
Serve the soup in small glasses or cups, and add the strips.