Preheat oven to 375. Line or grease and flour 12 muffin cups (see note).
In a large bowl, stir together flour, sugar, baking powder, baking soda and mace. In another bowl, stir together the oil, milk, ricotta, egg and vanilla until well-blended.
Make a well in the center of the dry ingredients and pour in the wet. Stir until just mixed (batter will be thick) then fold in the fruit. Spoon batter into the prepared tins and sprinkle with coarse sugar.
Bake 15-20 minutes or until toothpick inserted into the center of the center muffin comes out clean.
Remove to rack and let cool at 5 minutes. Invert on to rack and cool completely.