Add the onion, carrots, and potatoes to a medium-sized saucepan. Add enough chicken stock to cover the vegetables (about 1 1/2 - 2 cups) and cover with a lid. Bring to a boil and cook for about 10 minutes or until the vegetables are tender. Add the corn and peas for the last minute of cooking to thaw them. Drain when cooked.

Melt the butter in a Dutch oven. Whisk in the flour, salt, and black pepper. Cook until the mixture is bubbly and the flour lightly browns. Stir in the Better than Bouillon Roasted Chicken Base.

Add the chicken stock and half-and-half and cook until the sauce thickens and is smooth. Use a whisk to break up any lumps. The soup should be thick. If not, mix 1 tablespoon of cornstarch with 1 tablespoon of water and stir it into the hot soup, cooking until thick. Then add the cooked vegetables and chicken; stir to mix. Season with salt and pepper to taste. Top bowls of soup with a slice of baked puff pastry.