Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Make a lilac sugar by adding lilac blossoms and sugar to a mortar. Gently grind with a pestle until the flowers break down and release their oils. You can also do this in food processor.
In a large bowl, whisk together flour, lilac sugar, and baking powder.
Add the grated frozen butter and cut it into the flour mixture using a pastry cutter or your fingers until it resembles coarse crumbs.
In a separate bowl, whisk together the egg, yogurt, and vanilla.
Pour the wet ingredients into the dry ingredients and gently mix until just combined.
Make a well in the center of your dough and whisk in your egg and yogurt. Also, add your lilac 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 (any milk works here) 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.
cream cheese Icing:
Combine butter and cream cheese in the bowl of a stand mixer (or in a large bowl if you’re using an electric mixer) and beat until creamy.
Add vanilla and salt and stir well to combine.
Slowly add powdered sugar and mix with your mixer setting turned on low until completely combined.
Use an icing spatula to frost your scones Make sure scones are cool, otherwise the cream cheese icing will melt when you frost them.