Oatmeal Flax Muffins

(recipe adapted from here)
I have been looking for the perfect base recipe for different add-ins and I think I just found it. I like a flavorful, hearty, chewy and almost healthy muffin (but not quite...). None of those white fluffy things that people call muffins but they're really cupcakes.
This time, I threw in dark chocolate chunks and craisins. Mmmm, perfect! The original recipe called for blueberries. You can add whatever you like.

Ingredients:
1 cup rolled oats or old fashioned oatmeal
1 cup buttermilk (or regular milk + 1 teaspoon vinegar)
3 tablespoons unsalted butter, melted
2 eggs
2/3 cup brown sugar
1 teaspoon vanilla
1 cup flour
4 tablespoons ground flaxmeal
1 teaspoon baking powder
1 teaspoon baking soda
3/4 teaspoon salt
1 cup add-ins of choice (chocolate, craisins, berries, etc)

Directions:
Preheat oven to 375°. Grease a 12 cup muffin tin.
Combine the oats and buttermilk in a mixing bowl. Let the oats soak for 15-20 minutes. Add the melted butter, egg, brown sugar, and vanilla. Stir by hand until just combined.
Add the flour, flaxmeal, baking powder, baking soda, and salt. Stir again until evenly moistened.
(Whatever I'm adding in, I like do push them in by hand into each muffin cup to make sure they are evenly distributed. You can also pour them batter into the bottom of the cups, then stir them into the batter and pour the rest in. Or just mix them all in if you don't care if they're even.)
Bake for 13-15 minutes.