In mixing bowl, combine flour, sugar, salt and baking powder.

Add frozen butter cubes to dry ingredient mixture, and use hands or a pastry cutter to work butter into flour until you have pea-sized clumps of butter coated in flour.

In liquid measuring cup, whisk together buttermilk, egg, lime juice and lime zest. Pour mixture into bowl with butter and flour.

Add blackberries and gently stir with wooden spoon or hands until dough just comes together. (Note: Avoid overmixing to prevent tough scones.)

Transfer dough to lightly floured work surface and shape into a disc about 8 inches in diameter and 1/2-inch thick. (Note: Dough should be slightly sticky. If dough is dry, add buttermilk 1 Tbsp. at a time. If dough is too wet, add flour. Use floured hands to work with dough.)

Use bench scraper or sharp knife to divide disc into 8 wedges. Arrange wedges on parchment-lined baking sheet.

Refrigerate 15 minutes. Preheat oven to 400 degrees F.

Remove scones from fridge and brush with buttermilk. Bake 20-25 minutes or until golden brown on bottom and cooked through. Remove from oven and cool fully before adding glaze.

To make glaze, in small bowl, whisk together powdered sugar, milk and vanilla until smooth. For thicker icing, add more sugar 1 Tbsp. at a time. For thinner icing with drizzle consistency, add more milk 1 Tbsp. at a time.

When scones are cool, drizzle with glaze and serve.