1. Preheat oven to 350 degrees Fahrenheit. Line 12 muffin tins with liners or grease well with baking spray.
2. Spread the pecans on a baking sheet and toast in the oven for nine to 10 minutes.
3. Meanwhile, in a large bowl, stir together the first six dry ingredients, through salt. Make a well in the center and add in the egg, milk, oil, and vanilla extract; mix everything together until just combined. Stir in toasted pecans last.
4. In a small bowl, make the crumble. Mix together flour, brown sugar, and cinnamon. Add in oil and mix until crumble forms.
5. Using a large ice cream scoop, drop muffin batter into prepared muffin tins, filling 3/4 full. Sprinkle crumble evenly over each muffin. Bake muffins for 18-21 minutes for regular muffins or 23-26 minutes for large muffins, or until a toothpick inserted into the center of one comes out clean. Allow muffins to cool before removing from tins.