Preheat oven to 350ºF. Line 18 muffin cups with paper liners.
In a large bowl, mix together the wet ingredients.
In another bowl, combine dry ingredients
Stir dry ingredients into wet ingredients until well combined.
Optionally add in pecans and/or chocolate chips.
Fill muffin cup to 2/3 full.
Add optional streusel topping (see directions below).
Bake muffins in the preheated oven for 20-25 minutes, or until a toothpick comes out with dry crumbs.
Remove pans from oven and allow to cool 10 minutes before removing muffins from pan to cool completely.
Once muffins have cooled, drizzle on melted chocolate if desired.