01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, poppy seeds, lemon zest, baking powder, baking soda, and salt.
03 - Add cold cubed butter and blend into the dry mixture using a pastry cutter or fingertips until coarse crumbs form.
04 - In a separate bowl, whisk heavy cream, egg, lemon juice, and vanilla extract until combined.
05 - Pour wet ingredients into the dry components. Stir gently just until integrated, avoiding overmixing.
06 - Turn dough onto a lightly floured surface and pat into a 1-inch thick round.
07 - Slice the dough into 8 wedges and space them evenly on the prepared baking sheet.
08 - Brush the tops of the wedges with a little heavy cream.
09 - Bake for 18 to 20 minutes until golden brown and fully cooked. Transfer to a wire rack to cool.
10 - Whisk powdered sugar with enough lemon juice to achieve a thick yet pourable consistency.
11 - Drizzle the glaze over the cooled scones and allow it to set before serving.