Preheat oven to 425ºF. Grease 12-
cup muffin pan or use
silicone liners. Set aside.
Make homemade buttermilk: In a glass measuring cup, add milk + apple cider vinegar; set aside for about 5 minutes.
Prepare berries: Rinse and dry blackberries, then chop in half or thirds, depending on how large the blackberries are. Set these aside for later.
Make crumble topping: Combine crumble ingredients separately in small bowl and set aside.
Mix dry ingredients: In a medium bowl, whisk together flour, chai spices, baking powder, baking soda, and salt; set aside.
Mix wet ingredients: In a large bowl, whisk together oil with maple syrup. Add in egg and vanilla and whisk until combined. Pour half of the milk-vinegar mixture and gently stir to combine.
Combine: Add about half of the bowl of dry ingredients into the wet ingredients and begin to stir gently. Add the remaining flour and milk, along with the blackberries. Gently stir everything together until dry flour is no longer visible; Batter will be somewhat thick. Avoid over-mixing the batter or you'll end up with tough muffins.
Bake: Evenly distribute batter into 12-cup muffin pan, filling 2/3 full (about ¼ cup of batter). Sprinkle crumble mixture on top of batter in each cup, gently pressing slightly into batter. Bake muffins at 425ºF for 5 minutes; reduce oven temperature to 375ºF and continue baking for an additional 10-12 minutes, or until inserted toothpick in center of muffin comes out clean.
Cool: Allow muffins to cool in pan for about 10 minutes before gently removing. TIP: If greasing muffin pan, I use a butter knife to remove from pan. Transfer blackberry muffins to wire rack and allow to cool completely before storing.