Preheat your oven to 180C / 160C fan / gas mark 4 / 350F.
Put the butter in a small saucepan and melt gently on a very low heat. When all the butter is melted, turn off and leave to cool for a few minutes.
Line 2 small (1lb) loaf tins with loaf tin liners or greaseproof paper. (See Note 2.)
Next, tip the flour into a large bowl and add the bicarbonate of soda, salt and sugar. Stir to combine.
Peel the bananas and rip them into chunks. Place the banana chunks in a small bowl or jug. Use a potato masher to mash them roughly, then add the eggs and stir to combine.
Tip the eggs and banana mixture into the dry ingredients and stir thoroughly until you have a thick batter. Add the cooled melted butter and stir well.
Finally add the seeds or nuts, if you are using them, and stir once more until the seeds are evenly distributed.
Divide the mixture equally between the 2 loaf tins and cook the banana bread in your preheated oven for 45 minutes. Check they are cooked by inserting a skewer (or teaspoon handle) into the middle of your banana bread. If they are done, the skewer will come out clean. If not, cook your banana bread for a further 3 minutes and check again.
When your banana bread is cooked, remove from the oven. Allow to cool for 5 minutes, then remove from the tin. Peel off the liners / greaseproof paper and cool on a wire rack… or enjoy while it is still warm!
