To make the bread:

1. Preheat the oven to 350F. Grease an 9×5 loaf pan with baking spray.
2. In a large bowl, combine and whisk the dry ingredients: flour, baking soda, baking powder, salt.
3. Add in the sugar, kefir, and egg, and whisk until fully incorporated.
4. Add the vanilla extract and oil, and continue whisking until combined, careful not to over mix.
5. To a small bowl, add 1 tsp of flour and toss to cover the blueberries. This prevents the blueberries from sinking.
6. Fold in the blueberries.
7. Pour batter into prepared pan. Cover with the streusel topping.
8. Bake for 50 minutes, covering with a foil about halfway through. The quick bread is ready when a toothpick inserted in the center comes out clean.
9. Allow to cool before drizzling the icing on top.

Make the Streusel:

1. In a medium bowl, stir together the flour, sugar and brown sugar. Add the cold butter and using a pastry blender or fork (or your hands) mix until crumbly.

Make the Icing:

1. In a large bowl, sift the powdered sugar. Add the oil and one tablespoon of hot water at a time. Add a splash of vanilla and whisk together until desired consistency. Fill a medium sized ziploc bag, cut the corner and pipe the top of the cooled bread just before serving.