In a medium bowl, mix all ingredients for streusel topping and set aside.
In another bowl mix Evaporated Milk and vinegar and set aside for 5 minute to make buttermilk.
After 5 minutes, add oil, egg, brown sugar and vanilla essence to buttermilk mixture. Set aside.
In a large bowl mix flour, baking powder, salt and baking soda.
Pour buttermilk mixture into flour mixture to form muffin batter.
Gently fold in the chopped apples.
Pour batter into pre-lined muffin pans and top each muffin with streusel topping.
Bake in pre heated oven at 350°F (180°C) for 15-20 minutes or until golden brown.
Remove from oven and cool for 10 minutes before drizzling with caramel sauce.