Preheat oven to 350°F. Spread the slivered almonds onto a sheet pan in a single layer. Toast in the oven until lightly golden brown, about 5-7 minutes. Remove and cool completely.
In a medium skillet set over medium heat, melt the butter. Add the flour and whisk until it forms a thick paste (roux) with the butter.
Add the chicken stock a little at a time, while whisking constantly, and waiting until it is fully incorporated before adding more. Stir in the milk. Bring to a boil and simmer gently for 4-5 minutes until thickened and smooth, stirring frequently.
Combine the creamy chicken sauce, chicken, celery, green onion, mayonnaise, lemon juice and toasted almonds and dump into a medium or large greased baking dish. Combine the crushed potato chips and cheese and spread on top.
Cover with foil and bake in the oven until sauce is bubbling around the edges, about 25-30 minutes. Remove foil and bake until topping begins to brown, about 10 minutes more.
Serve immediately. Spoon over steamed rice, if desired.
Note: If desired you can use one 10-oz can of cream of chicken soup and skip Steps 2 and 3.
Calories: 685kcal, Carbohydrates: 17g, Protein: 45g, Fat: 49g, Saturated Fat: 15g, Cholesterol: 141mg, Sodium: 563mg, Potassium: 767mg, Fiber: 4g, Sugar: 3g, Vitamin A: 695IU, Vitamin C: 14mg, Calcium: 376mg, Iron: 3mg