Preheat oven to 4000°F or 204°C . Line a baking sheet with parchment paper.
Combine flour and baking powder in a large bowl and set aside.
Create a lavender lemon sugar by grinding your sugar, lavender, lemon zest, and vanilla extract together in a blender, food processor, or mortar and pestle. Set aside.
In a small bowl, whisk together your egg and yogurt.
Grate your frozen butter into your flour mixture an use a pastry cutter (or your fingers) to combine until they're crumbly, pea sized pieces.
Make a well in the center of your dough and whisk in your egg and yogurt. Also, add your lavender lemon sugar. Combine until a thick dough forms.
Place your dough onto your parchment lined baking sheet, pat into an 8-inch circle, and cut into 8 wedges with a sharp knife. Brush with your 2 tablespoons buttermilk. Arrange the wedges around the baking sheet, leaving room for rising and expansion while they bake.
Bake for 20 minutes, or until golden brown. Cool on a wire rack. Make your icing while your scones bake.
Icing: Add the powdered sugar, lemon juice, and vanilla extract to a small bowl and stir until combined. Drizzle over scones after scones have cooled for a few minutes.