Oven 180c.
Chop up the dates finely (easier with scissors) and add to a jug with the bicarb. Pour over just enough boiling water to cover, stir and set aside.
Mash the banana in a bowl with the sugar until broken down.
Add the vanilla, egg, yogurt and oil and beat together. Stir in the baking powder then flour.
Drain the dates then using a fork, mash these against the side of the jug to break them down. Stir into the batter.
Divide the batter between 6 muffin cases or use a silicone mould.
Bake for 25 mins. A skewer should come out clean.
Whilst the muffins are baking, add the butter sugar and cream to a pan. Heat gently, stirring occasionally until the sugar has dissolved. Simmer for 4 - 5 mins to thicken.
Leave the sauce to cool slightly then spoon over the cooked muffins. Serve warm or cold.