Preheat oven to 425 degrees F. Line a baking sheet with parchment paper or a silicone baking mat. Set aside.
Toss the peach slices with the sugar and liquor, if using. Set aside for 5 minutes.
Whisk the dry ingredients together in a large bowl. Set aside.
In a large measuring cup or a medium sized bowl, whisk the buttermilk, one egg, vanilla, and butter together until well combined. Pour the wet ingredients into the dry and stir with a baking spatula until just combined. Don't over mix or the biscuits will be hard and dense.
Beat the remaining egg with the splash of milk to create an egg wash. Drop ⅓ cup of dough onto a parchment lined baking sheet about 2-3 inches apart. Brush egg wash over the top of the dough and sprinkle turbinado sugar generously over the top.
Bake for 12-15 minutes. They should be lightly golden brown when done, don't over bake them. Cool the biscuits on a wire rack.
When ready to serve, whip the cold heavy cream, sugar, and vanilla with a hand mixer or whisk (and elbow grease!) until soft peaks form.
To serve, split one biscuit in half and top the bottom half with peaches and the accumulated juice, then add a hearty spoonful of whipped cream.