Preheat oven to 400°F (205°C) and line 12 muffin cups with paper liner.
Bring the lentils and porridge oats to a boil in a medium saucepan with 1 cup of water. Cook for 1 to 2 minutes and then set aside and allow to cool.
Whisk together the flour, sugar, baking powder, cinnamon, and salt in a large bowl. Once the oatmeal and lentils have cooled to a lukewarm temperature, stir in the milk, egg, and melted butter or oil. Add this mixture to the dry ingredients along with the blueberries and stir just until combined; do not worry about getting all the lumps out of the batter.
Fill the muffin cups and bake for 20 minutes, until pale golden and springy to the touch.