Preheat oven and prepare baking sheets: Preheat your oven to 400 degrees F. Line 2 baking sheets with parchment paper and set aside.
Mix wet ingredients: In a medium size bowl, whisk together the milk, eggs, vanilla extract, lemon zest and sugar. Set aside.
Mix dry ingredients: In a large mixing bowl, combine the flour with the baking powder and salt together.
Cut the butter with the flour: Cut the butter into the dry ingredients until the size of large peas, using a pastry blender. Stir in the wet ingredients, and mix until just combined.
Fold in blueberries: Sprinkle about 1 tbsp of flour over the blueberries and gently fold them in to the dough. The flour will prevent the blueberries from sinking to the bottom.
Shape scones: Transfer the dough to a lightly floured surface. Cut the dough in 2 pieces. Gently roll out each piece of dough into a disc, taking care not to burst the blueberries. Fold the dough over itself and repeat 4-5 times. Depending on the shape you want your scones, roll out your dough into an 1-inch thick disc or rectangle. Cut the dough into wedges (if shaped into a disc), or squares (if shaped into a rectangle), or cut out with a biscuit cutter. Repeat with the other piece of dough. Transfer scones to a baking sheet and brush with egg white.
Bake: Bake for 18 to 20 minutes, or until the scones are golden brown and do not fall apart when nudged. Immediately transfer from the baking sheets to cooling racks.
Make lemon glaze: Meanwhile, in a medium bowl, mix together the powdered sugar, milk, 1 teaspoon vanilla, and lemon juice. Stir until the mixture is smooth and runny. If too thick add more milk; if too thin add more powdered sugar.
Drizzle scones with glaze and serve: While scones are still warm, drizzle lemon glaze over each scone. Allow scones to stand for a few minutes until the glaze forms a crust, then serve and enjoy.
The Butter: Scones are all about the butter. Make sure your butter is really cold right out of the fridge. You could even freeze your butter before adding it to the flour. If using frozen butter, it might be easier to grate it instead of cutting it in with a pastry blender. The cold butter is what contributes to your scones being crisp and crumbly on the outside.
Storage: Store in an airtight container at room temperature for 1 to 2 days or in the fridge for up to 3 days. To freeze, wrap each scone individually in plastic freezer wrap or in a heavy duty freezer bag for up to 3 months.
Nutrition: Nutritional information is for 1 scone with lemon glaze. Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.