Place a pan on the stovetop over medium heat and, once hot, add the bacon to it. Let the bacon cook, flipping it occasionally, until crisp. Once finished, set the bacon aside.
While the bacon cooks, place the potatoes in a large pot, cover the potatoes in water, and bring to a simmer over high heat. Simmer for 20 minutes, or until the potatoes are easily pierced with a fork.
Drain the potatoes then add the butter, cream, salt, and pepper. Using a potato masher, mash the potatoes until smooth.
Preheat the oven to 350°F. Spread the potatoes out in the bottom of a 9x13 casserole dish (or any 3.5-4 quart dish).
For the chicken layer, mix the mayo with the lemon juice and dill in a large bowl, and whisk until smooth. Add the cooked, shredded chicken and toss to combine, then spread the chicken over the mashed potatoes.
Top the chicken with the shredded cheese and then sprinkle the bacon on the very top. Bake the casserole for 20 minutes, until the cheese is bubbly and the casserole is warmed through.
Top with fresh chives, then serve and enjoy!