Combine rolled oats, brown sugar, flour, cinnamon, salt, and butter in the bowl of a stand mixer fitted with a paddle attachment. Mix on low to form a crumbly meal, then fold in pumpkin seeds by hand. Transfer to a small bowl, cover with plastic, and freeze until needed, up to 1 month.

Adjust oven rack to middle position and preheat to 350?F (175?C). Combine whole wheat flour, all-purpose flour, sugar, cinnamon, ginger, baking powder, baking soda, salt, cloves, nutmeg, and butter in the bowl of a stand mixer fitted with a paddle attachment. Mix on low to form a mealy powder, about 2 minutes.

Add pumpkin pur?e, Greek yogurt, eggs, and vanilla, mixing only until dry ingredients disappear. With a flexible spatula, fold batter once or twice to make sure it's well mixed from the bottom up.

Lightly grease a standard muffin pan. Divide batter evenly between cups, filling each to the brim. Sprinkle generously with streusel, then bake until puffed and firm, about 25 minutes.

Cool at least 5 minutes before serving. Store leftovers in an airtight container for about 2 days.