Make filling: Melt butter, cook onion 4-5 minutes. Add garlic, cook 30 seconds.
Create sauce: Add flour, stir 1-2 minutes. Slowly add broth and milk, whisking constantly.
Thicken: Simmer 3-4 minutes until thick and creamy.
Add ingredients: Stir in chicken, vegetables, and all seasonings. Cook 3-4 minutes.
Cool: Transfer to bowl, cool completely (20 minutes minimum).
Prep: Preheat oven to 400°F. Line baking sheets with parchment.
Cut circles: Roll out crusts, cut 24 circles with 4-inch cutter.
Fill: Place 2-3 tablespoons filling on 12 circles, leaving ½-inch border.
Seal: Brush edges with water, top with remaining circles. Press and crimp with fork.
Prepare: Place on baking sheets, cut steam vents. Brush with egg wash, sprinkle with salt.
Bake: Bake 20-25 minutes until golden brown. Cool 5 minutes before serving.