TOPPING: In a small pan melt together first 4 ingredients over medium heat. Stir until mixed and remove from heat.
Grease muffin tin with non-stick spray (do not use liners).
Drain can of crushed pineapple, reserving liquid. Divide crushed pineapple between muffin cups and put on the bottom.
Put 4 blueberries on top of the pineapple on the bottom of each muffin cup. I used frozen berries but fresh or dried should work too.
Pour a tablespoon or so of brown sugar mix over the fruit in each cup.
CAKE: In a large bowl, mix flours and baking soda; set aside.
In a medium bowl beat butter and sugar together thoroughly.
Stir vanilla into butter/sugar mix, then add egg whites and beat well.
In a small bowl, combine the pineapple juice and yougurt, add milk and stir.
Fold the wet mixes into the dry in alternating fashion (between the butter/sugar mix and juice/milk mix).
Stir until it's just combined -- don't over mix.
Divide batter between muffin tins over fruit topping.
Bake for 20 minute or until muffin is done (toothpick inserted in the center should come out clean).
If eating immediately, let cool for 5 minute and run knife around the edge before transferring to plate. If eating later, chill in the refrigerator before removing from the pan (the topping comes out better this way).