Preheat the oven to 180C and grease and line 8 holes of a standard muffin tray.
In a large microwave safe bowl, melt the butter.
Stir in the caster sugar until smooth.
Add the egg, oil, milk and vanilla and stir until smooth.
Sift in the flowers and baking powder and stir until the batter is smooth and everything is evenly incorporated.
Add the salt and sprinkles and stir to mix through.
Divide the mixture evenly between the holes of the muffin pan.
Bake for 20-25 minutes or until the muffins are golden brown and an inserted skewer comes out clean.
Allow to cool completely before topping with whipped cream and more sprinkles, if desired.