Make crepes according to package instructions and set aside. Cover with a towel so they do not dry out.
In a sauté pan, add the butter and sauté the mushrooms until tender. Add the flour and stir to coat the mushrooms. Begin whisking in the milk and bring to a simmer. Let the mixture thicken and lower the heat. Add the salt and pepper. Taste for seasoning. Remove 1/2 cup of sauce and set aside. Stir the chicken into the remaining sauce.
Lay a crepe flat on the counter. Add a 1/4 of the chicken and mushroom mixture to the middle of the crepe. Roll like a burrito and place in a greased 8 x 8 baking dish. Repeat with the remaining crepes. Pour the reserved sauce over the top.
Bake for 20 minutes at 375 degrees.