Set your oven to 400°F (200°C). Grease your baking dish with butter or non-stick spray.

In a skillet, melt margarine over medium heat. Add chopped onions and cook for about 5 minutes until soft. Reduce heat to low and continue cooking for 35 to 40 minutes, stirring occasionally, until deep golden brown.

In a large pot, bring chicken broth to a boil. Add chicken breasts, reduce to a simmer, and cook for about 20 minutes or until fully done (internal temperature 165°F or 74°C). Remove chicken with a slotted spoon and set aside. Reserve the broth for the potato mixture.

Using an electric juicer, extract juice from the potatoes. Discard the liquid and place the dry potato pulp into a large bowl.

No juicer? Grate the potatoes manually and wring out the juice using cheesecloth or a clean towel.

Add salt and pepper to the potato pulp. Slowly stir in the hot reserved broth until the texture resembles warm oatmeal. It should be thick but still spreadable.

Spread half of the potato mixture into the greased baking dish.

Shred or slice the cooked chicken and distribute it evenly over the potatoes.

Add the caramelized onions as the next layer.

Top with the remaining potato mixture, smoothing it to cover the filling entirely.

Bake the assembled dish uncovered at 400°F for about 1 hour, or until the top is golden and lightly crisped.

Let the pie rest for about 10 minutes before slicing. For added moisture and flavor, reheat some of the reserved broth and ladle it over each serving.