Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish with butter or non-stick spray.

Place the washed and scrubbed potatoes directly on the oven rack and bake for 45-60 minutes, or until tender. Let them cool slightly.

In a saucepan over medium heat, melt the butter and cook the garlic for 1 minute. Stir in the flour and cook for another minute, stirring constantly.

Gradually whisk in the milk, stirring continuously until smooth and thickened. Remove from heat and stir in 1 cup of shredded cheddar cheese and sour cream. Season with salt and pepper to taste.

Slice the baked potatoes in half lengthwise and scoop out the flesh, leaving a thin layer in the skins. Place the potato shells in the prepared baking dish.

Dice the scooped-out potato flesh and combine it with the cooked chicken, blanched broccoli, and cheese sauce. Stir until well combined.

Spoon the chicken, broccoli, and cheese mixture into the potato shells, dividing evenly. Sprinkle the remaining shredded cheddar cheese on top.

Bake for 20-25 minutes, or until the cheese is melted and bubbly. The top should be golden brown.

Let the casserole cool slightly before serving. Garnish with fresh chives or green onions if desired. Enjoy warm!