Preheat oven to 375 degrees and line two baking sheets with parchment paper.

Whisk the flour, sugar, baking powder and 3/4 teaspoon salt until combined.  Cut the butter into 1/2"  pieces, then cut into the flour mixture using a pastry cutter or two knives.  If using the two knives, cut across the pieces of butter in opposite directions until it resembles a coarse meal, about pea size chunks.  Gently stir in the blueberries.

Slowly pour in most of the buttermilk, gently folding the mixture until there are no more bits of flour remaining in the bottom of the bowl.  You want the dough to be moist and slightly sticky, if the dough is dry then add the remaining buttermilk, a couple of tablespoons at a time.  Just don't overdo it or you will have a gloppy mess!

Using a large spoon, or even better a 1/4" cup ice scream scoop, scoop mounds of dough onto the parchment lined baking sheets, placing the Biscones about an inch apart.  

Now to add the golden touch, lightly beat an egg with a Tablespoon of water.  Brush the tops of the Muffins liberally with the egg wash.  Bake for 20 to 25 minutes, until the Muffin Tops are golden and fully baked.  Remove from the oven and let cool for 10 minutes.

While Muffin Tops are baking, stir the confectioners' sugar with the grated lemon zest and juice until smooth and creamy. Drizzle over the muffins and serve immediately.

If eating later wait until the muffins are completely cool before adding the glaze.