Preheat the oven to 375°F (190°C). Grease a standard 12-cavity muffin mold. If using silicone, place it on a metal baking sheet before filling.
Combine the dry ingredients. Whisk the flour, sugar, baking powder, baking soda, and salt in a large bowl.
Mix the wet ingredients. In a separate bowl, whisk the buttermilk, eggs, melted butter, and vanilla until combined.
Make the batter. Pour the wet mixture into the dry ingredients and gently fold just until a few streaks of flour remain. Fold in the freeze-dried blueberries, scraping in any blueberry powder as well. Avoid overmixing; small lumps are fine.
Fill the mold. Divide the batter evenly among the 12 cavities, filling each approximately three-quarters full. Bake promptly so the berries don’t sit absorbing moisture from the batter.
Bake for 16–20 minutes, until the tops spring back gently when touched and a toothpick inserted into the centre comes out clean. They may remain fairly pale; avoid waiting for deeply golden tops. Silicone molds may need a few additional minutes.
Cool and serve. Let rest in the mold for 5–10 minutes before carefully removing. Serve warm with butter and maple syrup.