• Preheat the oven to 400°.
• In the bowl of a food processor, combine flour, baking powder, salt, and sugar. Pulse to combine. If you don't have a food processor, whisk in a large bowl to blend. Add lemon zest and pulse again to combine or whisk into the flour mixture if using a bowl.
• Add chilled cubed butter and pulse until butter is mixed with flour into coarse crumbs. If you don't have a food processor, cut butter into flour mixture with a pastry cutter or forks until mixed into coarse crumbs. (Sometimes, I use my clean fingers to press the butter into flour, crumbling between fingers, so no large butter chunks remain.)
  
• If using a food processor, dump the flour and butter mixture into a large bowl. Gently toss in dry blueberries.
• Whisk cold cream and egg together in a measuring cup.
• Make a well in the center of the blueberry and flour mixture. Pour cold cream and egg mixture into the well and gently scrape and pull spoonfuls of flour into the cream to mix and turn over. Stir and scrape carefully to mix but not crush the blueberries until all flour mixture is incorporated.
  
• When the dough has just come together and is sticky, scrape it onto a piece of parchment paper and carefully press dough together into a circle about 7 inches in diameter.
  
• Wrap the circle in parchment and refrigerate for 10-15 minutes to chill and gently firm the dough.
• When 10 minutes is up, remove the dough and open it onto a cool pastry board, marble counter, or cutting board lightly dusted with flour.
• Cut the dough into triangles like a pizza and place each scone on the parchment-lined baking sheet. Lightly brush the top of each scone with heavy cream.
  
• Bake for 20-23 minutes until the tops are lightly brown across the top. Test through the middle with a toothpick. If the toothpick is wet, or squish down in the center if tapped with a finger, let your scones bake for 1-2 more minutes as needed.
• Cool the scones on the sheet pan for a few minutes. Then transfer the scones to a cooling rack while you make the glaze.

Lemon Glaze

• Whisk together lemon juice and sifted powdered sugar until no lumps remain.
• Melt butter and whisk warm melted butter into the glaze.
• Set scones on a cooling rack over a cookie sheet to collect the drips. Drizzle warm glaze over the scones as desired. Let glaze set for a couple of minutes before serving.