In a small bowl, mix cornstarch thoroughly with 1 teaspoon cold water. In a large bowl, combine mixture with soup, and mix thoroughly. Add vegetables and chicken, mix well, and then season to taste with salt and pepper. Set aside.
On a large dry surface, lay out three egg roll wrappers. Set out a small bowl of water, dip your fingers into it, and then run your finger along all of the wrapper edges - repeat this as needed while preparing your pockets to help keep them sealed.
Starting about 1/2 inch from the bottom, pace about 1/3 cup filling along the bottom half of each wrapper, leaving 1/2 inch boarder on both sides. Fold the top half of each wrapper over, so that the top edge meets the bottom - the mixture should be completely encased with a 1/2 inch border on three sides. Dab each border with water, and fold each inward about 1/4 inch to lightly seal all sides. Press firmly along the borders with the prongs of a fork to seal.
Line a large baking sheet with foil and/or spray with nonstick spray. Using a large spatula, carefully transfer the pockets to the baking sheet. Repeat the entire process 3 more times, so that you have 12 pockets on the baking sheet. If needed, prepare and use an additional baking sheet.
Bake in the oven for 20 minutes. Allow to cool for 5 minutes before serving.