Preheat oven to 400°F (200°C). Pierce potatoes several times with a fork.
Bake potatoes in the preheated oven for 1 hour, or until tender.
While potatoes are baking, blanch broccoli florets in boiling water for 3 minutes. Drain and set aside.
Once potatoes are cooked, let them cool slightly. Cut each potato in half lengthwise.
Carefully scoop out the flesh from each potato half, leaving about a ¼-inch shell. Place the shells on a baking sheet.
In a medium bowl, mash the scooped potato flesh with a potato masher or fork. Stir in the buttermilk, half of the cheddar cheese, salt, and pepper until well combined.
Gently fold in the blanched broccoli florets into the potato mixture.
Spoon the potato and broccoli mixture back into the potato shells.
Top each filled potato shell with the remaining cheddar cheese.
Bake for 15-20 minutes, or until the cheese is melted and bubbly and the potatoes are heated through.
Notes
Optional: Garnish with chopped chives or a dollop of Greek yogurt before serving.