Preheat an oven to 190 degrees C. Grease 24 mini muffin cups or 12 standard muffin cups.
In a mixing bowl, beat together the butter and brown sugar until smooth. Mix in the mashed bananas, pumpkin baby food, carrots and eggs. Stir in the flour, oat bran, baking soda, mixed spice and salt until just combined. Spoon the batter equally into the prepared muffin cups.
Bake in the preheated oven until a toothpick inserted into the centre comes out clean, 15 to 20 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack. Store at room temperature for up to two days or freeze.
I always keep a supply in the freezer, my son loves them frozen especially when new teeth are coming in!