Place the wheat germ in a heavy-bottomed skillet over medium heat and toast, stirring continuously, until nutty brown, about 7-8 minutes. Immediately remove from skillet to stop the toasting.

In the bowl of a stand mixer fitted with the paddle attachment, mix together wheat germ, flour, oats, sugars, cinnamon, nutmeg, and salt, for about 1 minute. Scrape seeds from vanilla bean and mix in until well combined, another minute. Add butter and mix on low until no large chunks remain, about 1-2 minutes.

Transfer to a airtight container and refrigerate at least 2 hours, preferably overnight.

In a medium bowl, whisk together flour, baking soda, baking powder, cinnamon, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, mix together sugar and oil for 1 minute.

Add eggs and mix until incorporated, about 1 minute.

Add flour mixture in two additions, mixing on low until just combined.

Scrape down bowl and stir in carrots.

If making mini muffins, transfer batter to a piping bag; otherwise, transfer to an airtight container and refrigerate overnight.

If making mini muffins, preheat oven to 350°F. For regular-sized muffins, preheat over to 425°F. Line muffin pans with papers.

Fill each paper, stopping about 1/4 of an inch from the top. Sprinkle a generous amount of streusel on top and press in lightly.

For mini muffins, bake for 18 minutes, or until a skewer inserted into the center comes out clean.

For regular muffins, place in the oven, immediately lower the heat to 325°F, and bake 30-35 minutes, or until a skewer inserted into the center comes out clean.

Transfer to a rack to cool completely.