Preheat oven to 400.
In large bowl sift together flour, sugar, oats, baking powder, salt, nutmeg and baking soda.
In medium bowl whisk together buttermilk (or yogurt), butter, molasses and egg.
Stir wet ingredients into dry ingredients until just combined. Add chopped and pitted prunes and stir again.
Divide batter evenly among 12 greased or paper-lined muffin cups.
Place muffins in preheated oven for 20-25 minutes, until golden and springy when touched.