Preheat the oven to 350°F. Line a muffin tin with liners.

In liquid measuring cup, measure non-dairy milk and whisk in apple cider vinegar. Set aside for 5 minutes.

In a large mixing bowl, whisk together the milk mixture, yogurt, oil, vanilla extract, and sugars until combined. Add flour, flaxseed meal, baking powder and soda, spices, and salt. Use a wooden spoon or spatula to fold dry mixture into wet until a smooth batter forms. Fill each muffin liner a little more than ¾ full.

Bake muffins for 20 minutes until top is golden brown and toothpick inserted comes out clean (a few moist crumbs is ok). Allow muffins to cool in liners for 5 minutes before removing and transferring to a wire cooling rack. Allow muffins to cool completely before frosting.

While muffins are cooling, prepare the cooked apples. In a medium saucepan, combine chopped apples, brown sugar, lemon juice, and spices. Bring mixture to a simmer and cook for 6-7 minutes until apples become soft. Once apples are soft, mix in vanilla extract and corn starch. Cook for 1-2 minutes more until juices surrounding the apples start to thicken and become syrupy.

Transfer apples to a bowl and set aside to cool.

In a small skillet, whisk together the oats, flour, brown sugar, cinnamon, and salt. Add butter and melt over medium-high heat. Stir in the butter as it starts to melt. Cook for about 1-2 minutes until butter is fully incorporated into dry mixture. Pour into a bowl and set aside.

In a large mixing bowl, add the softened butter and non-dairy milk. Sift over the powdered sugar. Use a whisk over handheld electric mixer on low to combine ingredients until a creamy frosting forms. Whisk in vanilla extract.

Frost each muffin and top with 1 tbsp stewed apples and sprinkle over streusel. You may need to press the streusel into the frosting in order for it to stick. Enjoy!