Preheat oven to 425°F (218°C). Line a muffin tin with paper liners.
Mill your whole grain into flour using the mill's finest setting. I used whole Einkorn berries and an electric countertop grain mill set on number 1. (See video.)
Mix the dry ingredients. In a large bowl, whisk together the Einkorn flour, wheat bran, baking powder, baking soda, and salt.
Add the raisins (and nuts if using) to the dry ingredients and toss to fully coat.
In a separate bowl, whisk the eggs, buttermilk, maple syrup, melted butter, and vanilla extract.
Add the wet ingredients to the dry ingredients and stir until just combined.
Scoop the batter evenly into the muffin cups.
Let the batter rest for 5 minutes.
Bake at 425°F (218°C) for 5 minutes, then reduce the temperature to 350°F (177°C) and bake for an additional 15–18 minutes, or until a toothpick inserted comes out clean.
Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.