To avoid DRY muffins, measure the flour properly by spooning it into your measuring cup and then, once the flour is "heaping" in the cup, level it off with a knife.
Turbinado sugar is also sold under the brand name, Sugar in the Raw. Using it along with the brown sugar in the crumble will add a great crunch!
Biscoff Spread (an alternate spread to nut butters or chocolate spread) is available in the Peanut Butter aisle in retail, club and drug stores nationwide as well as at
www.shopbiscoff.com; you can also the
Biscoff site for a more comprehensive list of stores that carry Biscoff products.
The crumble and the glaze are completely optional -- these muffins are still delicious without them and definitely hold their own. But ... I prefer "over the top" coffee cake and developed this recipe with the same philosophy!!