1. Preheat your oven to 400 F (200 C). Scrub the Russet potatoes clean under running water. Pat them completely dry, then rub each potato with about 1/2 tablespoon of olive oil. Pierce each potato several times with a fork. Place them directly on the oven rack and bake for 45-60 minutes, or until they are tender when squeezed and easily pierced with a fork.

2. While the potatoes are baking, prepare your chicken and broccoli. If using raw chicken, cook it now (e.g., pan-fry, bake, or boil) until fully cooked, then shred or dice it. Steam or lightly blanch the broccoli florets until tender-crisp, then set aside.

3. In a large saucepan or skillet, melt the butter over medium heat. Once melted, whisk in the flour and cook for 1-2 minutes, stirring constantly, to create a roux. This will thicken your sauce.

4. Gradually whisk in the milk, a little at a time, ensuring no lumps form. Continue whisking until the sauce thickens and comes to a gentle simmer, about 5-7 minutes. Stir in the garlic powder, onion powder, salt, and pepper. Remove from heat, then stir in 1 cup of the shredded cheddar cheese and the sour cream (or Greek yogurt) until smooth and well combined.

5. Gently fold the cooked shredded chicken and steamed broccoli florets into the creamy cheese sauce. Taste and adjust seasonings if needed.

6. Once the baked potatoes are ready, carefully remove them from the oven. Using oven mitts, slice each potato lengthwise down the middle, being careful not to cut all the way through. Fluff the inside flesh with a fork. Spoon a generous amount of the creamy chicken and broccoli mixture into each potato.

7. Sprinkle the remaining 1/2 cup of shredded cheddar cheese over the stuffed potatoes. Return them to the oven for another 5-10 minutes, or until the cheese is melted and bubbly.

8. Carefully remove the stuffed potatoes from the oven. Garnish with fresh chopped chives or green onions, if desired, and serve immediately.