Preheat oven to 375 degrees and line muffin tin with paper liners.
Prepare flax egg in a large mixing bowl and let set for a few minutes.
Add sweet potato purée, brown sugar, oil, and vanilla extract and mix. Then add almond milk and stir once more.
Carefully place whole wheat flour, baking powder, baking soda, salt and cinnamon into a sifter and sift over wet ingredients. Then add oat flour on its own (as it does not sift well in my experience) and stir until just combined.
Spoon batter into muffin tins until filled almost to the top. Then drop about 1 tsp almond butter onto the center of each muffin and gently swirl around with a toothpick or knife.
Bake for 20-22 minutes (or more) until golden brown and a toothpick in the center comes out clean.
Remove from oven and let rest in tins for 5 minutes. Then transfer to a cooling rack to let cool completely.
Store in an air-tight container and refrigerate to ensure freshness. Will keep in the freezer for up to a few weeks.