Set to 350°F (175°C) and line a muffin tin with paper liners.
In a small bowl, mix flour, brown sugar, and cinnamon. Add vegetable shortening and use your fingers or a fork to cut it into the dry ingredients until the mixture resembles coarse crumbs. Set aside.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and cinnamon.
In another bowl, combine non-dairy milk, oil, apple cider vinegar, and vanilla. Let the mixture sit for a couple of minutes to allow the vinegar to react.
Add the wet ingredients to the dry ingredients and mix until just combined (don’t overmix).
Spoon the batter into the muffin cups, filling them about ⅔ full.
Sprinkle the prepared streusel generously on top of each muffin.
Bake for 18-22 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool before adding the glaze.