Start by preparing all your ingredients: peel and dice the potatoes into 1-inch cubes and place them in cold water to soak (this removes excess starch and helps them cook evenly). Cut the chicken breasts into 1-inch chunks as specified. In a small bowl, combine the paprika, garlic powder, onion powder, salt, and pepper to create your seasoning blend. Toss the chicken pieces with the olive oil and season generously with the spice mixture, then let rest for 15 minutes at room temperature—this allows the seasonings to penetrate the meat and helps it cook more evenly.

While the chicken rests, drain the soaked potatoes and place them in a large pot of salted water. Bring to a boil and cook until the potatoes are fork-tender, about 15-20 minutes depending on their size. Start this step early so the potatoes finish cooking around the same time as your chicken and sauce, allowing everything to come together smoothly. Drain the potatoes well when done, reserving the pot for mashing.

Heat a large skillet over medium-high heat. Working in batches if needed to avoid overcrowding, sear the seasoned chicken chunks for 3-4 minutes per side until golden brown—don't stir too frequently, as this allows a flavorful crust to develop. Once the chicken is browned on all sides, reduce the heat to medium-low and add 3 tablespoons of butter along with the 1.5 tablespoons of minced garlic. Cook for about 1 minute, stirring constantly, until the garlic becomes fragrant but doesn't burn. Transfer the chicken to a bowl and cover to keep warm.

In the same skillet with the pan drippings, add 2 tablespoons of butter and the 9 cloves of freshly minced garlic, cooking over medium heat for about 1 minute until very fragrant. Pour in the chicken broth and heavy cream, stirring well to combine and scrape up any flavorful browned bits from the bottom of the pan. Simmer for 3-5 minutes until the sauce begins to thicken slightly. I like to taste the sauce at this point and adjust the seasoning if needed—the depth of flavor really develops as it simmers. Stir in the red pepper flakes, sliced green onions, and grated Parmesan cheese, stirring until the cheese melts and the sauce becomes creamy and cohesive. Add the lemon juice for brightness and the fresh parsley for color. Return the cooked chicken to the skillet, gently folding it into the sauce to coat evenly.

Once the potatoes are tender and drained, return them to the warm pot. Add 8 tablespoons of unsalted butter and the warmed half-and-half, then mash until you reach your desired consistency—I prefer leaving mine a bit chunky for texture, but you can mash them as smoothly as you like. Fold in the freshly shredded Monterey Jack cheese and season with salt and pepper to taste. The cheese will melt beautifully into the warm potatoes, creating a creamy, flavorful base for the chicken and sauce.

Divide the creamy mashed potatoes among serving bowls or plates. Ladle the garlic Parmesan chicken and sauce generously over the potatoes, ensuring each portion gets plenty of the rich, garlicky sauce. Serve immediately while everything is warm and the flavors are at their peak.