Pre-heat the oven to 200°C (400℉), and grease a six-hole muffin tray (or line with cases).
Beat butter, sugars and oil together, then beat in the egg and vanilla.
Add the baking powder, baking soda, nutmeg and cinnamon and stir until just combined.
Stir in half of the flour, then half of the milk. Repeat with the remaining flour and milk.
Fill the muffin cases (or muffin tin holes) half way up with batter.
Dollop one teaspoon of jam on top of each.
Cover the jam with the remaining batter.
Bake in the lower part of the oven for around 17 minutes. They are ready when an inserted skewer comes out (almost) clean.
Allow the muffins to cool for around ten minutes (or until you can handle them).
Melt the butter and brush over the still warm muffins.
Mix the cinnamon and sugar and dip the muffins in. Roll them about a bit until there is an even coverage. Enjoy!