Preheat oven to 400 degrees. Line a baking sheet with parchment paper.
In a bowl, mix together flour, brown sugar, baking powder, and salt. Once combined, cut in the butter with a fork or pastry cutter until the mixture resembles coarse crumbs.
Whisk together heavy cream, sour cream, egg, and vanilla extract. Slowly add the wet ingredients into the dry ingredients, and mix until just combined.
Stir in the peaches, and mix until just combined.
On a well-floured surface, turn out the scone dough and pat into a small disk that's about a 1/2" thick. Cut into 6-8 slices, and transfer to the baking sheet. Brush each scone with just a bit of heavy cream.
Bake for 16-18 minutes, or just until golden brown. Allow to cool.