1. Preheat the oven to 190C. Grease the muffin tin. Place the butter and sugar in a bowl and beat until a creamy texture.
2. Add one egg and beat in, then add the other and beat in. Add the cinnamon. Gradually add the flour and milk, alternating the two and beating to achieve a smooth texture.
3. Add the porridge oats, mash the bananas very well with the back of a fork, and add to the mixture and blend in well.
4. Spoon the mixture equally in the muffin tin moulds, filling to about 3/4 full.
5. Bake in the centre of the oven for about 20 minutes (checking and if necessary turning after 15 minutes). The muffins should be springy to the touch and fall out of the inverted tin quite easily.