Preheat oven to 180 degC

Whisk together the egg and sugar until fluffy. Sift the dry ingredients into a large bowl and make a well in the centre.

Melt butter and treacle in a small pan, cool a little then stir into dry ingredients along with egg and sugar mixture.

Bring milk to the boil and stir into the micture - mix well. Add and blend in sour cream.

Spoon into muffin cups, bake for 20 minutes untill well risen, firm and springy to the touch. Cool on wire rack.