Preheat oven to 400°F. Lightly spray or grease a muffin tin with oil. Set aside. In a large bowl, combine oats and milk. Let sit 15 minutes.
In a second mixing bowl, whisk flour, baking soda, baking powder, salt, and cardamom.
Stir the oil, egg, brown sugar and vanilla into the soaked oat mixture. Add dry ingredients. Stir just until combined. Do not over mix. Gently fold pears into the batter.
Spoon the batter evenly into the prepared muffin tin. (If using the crunchy topping: Stir the butter and sugar until the brown sugar dissolves. Top the muffin batter evenly with the mixture.)
Bake 12 minutes. Remove from the oven. Let the muffins cool in the pan 5 minutes. Transfer to a cooling rack. Enjoy these muffins warm or freeze for later.