Add all the muffin ingredients (except the blueberries) to a food processor and pulse until smooth. Divide between the prepared muffin tins. Divide the blueberries between the muffins and press down slightly.
Add the topping to the food processor and pulse until crumbs form. Do not process too long or it will turn into a dough. Scatter the crumbs on top of the muffins.
Bake for 30 minutes or until golden and firm to the touch. If the crumbs are getting too brown you can loosely cover the tray with aluminum foil.
Notes
If you'd like to reduce the carbs or calories you can leave off the crumb topping OR just make these into muffin tops by having the batter and baking in a muffin top pan. That way you still get the crumb topping but reduce the carbs by almost half.Notes on Sweeteners: