1Preheat the oven to 375°F.
2In an 8-inch square (or similar-sized) baking dish, mix together the oats, lentils, baking powder, cinnamon, and salt. Scatter with berries.
3In another bowl, whisk together the milk, maple syrup, egg, butter and vanilla. Pour the mixture over the oats, and give it a gentle stir to distribute everything evenly.
4Bake for 40 minutes, or until the top is golden and the oats have set. Serve warm, topped with milk or a splash of cream. Leftovers reheat beautifully.