Preheat oven to 375 degrees
Get 3 main work bowls ready (I use a small, medium and large).
Mix the milk with the vinegar or lemon juice and set aside to curdle. I use my glass pyrex measuring cup. This will be your vegan "buttermilk". It only takes a few minutes.
Bowl #1: Make your streusel: Mix together the streusel ingredients in a small bowl. Cut the butter or applesauce into the flour/sugar mixture. I use a pastry cutter, but alternatively you can use two knives, or even your clean hands. You want it to look like small pebbles.
Bowl #2: In the larger bowl, mix the dry ingredients: flour, sugar, baking powder, salt, cinnamon, and nutmeg. Stir in optional walnuts.
Bowl #3: Mix together your wet ingredients: the curdled milk, applesauce and mashed bananas.
Add your wet ingredients from bowl #3 to your dry ingredients to bowl #2 and mix just until combined. You don't want to over-mix.
If the batter looks too thick, add a bit more milk. If it looks too wet, add more flour. It should be a bit thicker than the consistency of banana bread batter.
Fill muffin cups 2/3 full. I use a medium cookie scoop for this, and I bake these in silicone muffin liners as described in my post.
Carefully sprinkle the streusel you made earlier over the muffins. You may find it easier to use your hands.
Bake for 15-20 minutes, checking after 15 minutes. They will be done when a toothpick inserted in the middle comes out clean. Let cool for about 10 minutes in pans before transferring to a wire cooling rack. Enjoy! Super yummy warm out of the oven with a cold glass of plant-based milk. Enjoy! <3 Amy