Preheat the grill to a medium setting.
Grill the sausages for 10-15 minutes on a baking tray until golden-brown, turning halfway through.
Cool the sausages slightly and slice them into bite-sized pieces.
Melt the butter in a large saucepan over medium heat.
Fry the diced onion and carrot for 8-10 minutes until softened.
Add the garlic and thyme sprigs and fry for 2 minutes until aromatic.
Stir in the drained lentils.
Pour in 1 liter of stock and roughly mash the lentils with a potato masher.
Add the sliced sausages and simmer gently for 10 minutes until slightly thickened.
Remove the thyme sprigs, season with salt and pepper, and serve hot.