Heat the oil in a large, heavy-based saucepan and cook the peppers, onion, garlic and fennel over a medium-high heat, stirring frequently, for 5 minutes until softened and lightly browned. Stir in the lentils, stock and wine and bring to the boil, then reduce the heat and simmer for 25 minutes until the lentils are tender.
Meanwhile, beat the softened butter with the garlic and thyme in a bowl and season with a little salt and pepper. Cut the baguette into thick slices, almost all the way through but leaving the base attached. Spread the butter thickly over each slice, then wrap the baguette in foil and place in a preheated oven, 200°C (400°F), Gas Mark 6, for 15 minutes.
Serve the stew hot, ladled into warm serving bowls, with the torn hot garlic and herb bread on the side for mopping up the juices.