Preheat oven to 375°F. Unroll pie crusts. On lightly floured surface, roll out each crust to 13-inch diameter. Cut five (5-inch) rounds from each crust. A small bowl that measures about 5-inches across works great.
Gently press crusts floured-side-down in bottoms and up sides of 10 ungreased muffin cups.
In a medium saucepan, melt butter over medium heat; add onion and cook 3-4 minutes, until onion is tender. Stir in flour until blended. Add milk, sage, salt and pepper. Cook 2-3 minutes, stirring, until mixture thickens.
Stir in chicken and mixed vegetables. Fill each muffin cup with ¼ cup chicken mixture. Fold and crimp pie crust over filling leaving the center open.
Bake 25-30 minutes until crusts are lightly browned. Cool 5 minutes; carefully run knife around each edge to loosen.