Preheat oven to 400 degrees F. Grease twelve 2-1/2-inch muffin cups; set aside.
In a large bowl combine flour, brown sugar, baking powder, cinnamon, salt. Make a well in center of flour mixture; set aside.
In a medium bowl combine banana, milk, melted butter, egg, and vanilla. Add banana mixture all at once to flour mixture. Stir just until moistened (batter should be lumpy). Fold in blueberries.
Spoon batter into prepared muffin cups, filling each about 3/4 full. Spoon 1 teaspoon pineapple jam in batter in each muffin cup. Bake 15 to 20 minutes or until golden and a wooden toothpick inserted in centers comes out clean. Cool in muffin cups on wire rack for 5 minutes. Remove from muffin cups; serve warm with additional pineapple jam, if desired. Makes 12 muffins.