Cook the bacon until crispy, drain on paper towels, and crumble into small pieces once cooled.

Whisk the flour, baking powder, salt, and sugar together in a large mixing bowl until well combined.

Cut the cold butter into the flour mixture using a pastry cutter or forks until it resembles coarse crumbs.

Stir in the shredded cheddar cheese, chopped chives, and bacon crumbles until evenly distributed.

Pour in the cold milk and fold gently with a spatula until a shaggy dough just begins to form.

Turn the dough onto a floured surface and pat into an eight-inch disc about one inch thick.

Cut the disc into eight even triangles and place them on a prepared baking sheet.

Brush the tops of each triangle with a mixture of beaten egg and water for a golden finish.

Bake in a preheated oven until the tops are golden brown and the edges feel firm to the touch.

Allow the scones to rest on the baking sheet briefly before serving them warm.