Cream butter and sugar until light and fluffy.
Add the eggs one at a time and continue beating .
Add in the mashed bananas .
Dissolve the bicarb in the milk and add the vanilla as well.
Add to the mixture alternately with the flour.
Fold in the raisins.
Place in a cake tin or line your slow cooker with baking paper and place directly in. A 3 litre cooker is perfect size.
Cook on high for 2 hours approx, depending on how hot your cooker cooks. Tea towel under the lid.
Check with a skewer if it comes out clean from the centre it's done.
If you notice the outside browning too quick before the middle is cooked then turn to low and continue until done.
When cold ice with lemon icing and sprinkle with cinnamon.