To make the streusel topping: In a medium bowl, stir together the flour, oats, brown sugar, and pecans. Using a fork, cut in butter until well combined and mixture begins to hold together a bit. Set aside.
Preheat the oven to 375°F Butter a 12-cup muffin tin. Place the dates in a shallow bowl (in a single layer if possible), pour the boiling water over them, and soak for 15 minutes. Transfer the dates and soaking liquid to a food processor and puree until almost smooth but a few pea-sized fruit pieces remain. Set aside to cool slightly.
In a medium bowl, combine the flour, baking powder, and salt. Set aside.
In the bowl of an electric mixer, cream together the butter and brown sugar. With the motor running, mix in the eggs, one at a time. Add the vanilla. Add half of the flour mixture and mix until moistened. Follow with the date puree, and when thoroughly combined, mix in remainder of the flour mixture. Scrape down the sides and give a final stir with a spatula to make sure all ingredients are thoroughly combined. Divide the batter among the muffin cups. Top with the streusel and press down gently to adhere. Bake for 20 to 25 minutes.