01 - Preheat oven to 450°F. Place butter in 8x8-inch baking dish and melt in oven while preheating, about 5 minutes.
02 - Remove dish from oven, swirl butter to coat bottom, and stir in peach preserves until combined.
03 - Whisk together flour, baking powder, sugar, and salt in large bowl.
04 - Pour cold milk into dry ingredients and mix gently until just combined. Do not overmix.
05 - Pour dough over peach butter in baking dish. Spread evenly to corners; dough will be wet and shaggy.
06 - Use greased knife or bench scraper to score dough into 9 squares in 3x3 grid pattern.
07 - Bake 22-25 minutes until golden brown on top and set in center.
08 - Whisk powdered sugar, milk, and vanilla extract until smooth and pourable.
09 - Cool biscuits 10 minutes, then drizzle vanilla glaze generously over warm biscuits.