Preheat the oven to 400°F.
Pierce the potatoes several times with a fork. Place in the microwave and use your baked potato setting until the potatoes are cooked through, turning half way. (Or you can bake 1 hour in your oven at 425° F)
While the potatoes are baking, chop all of your veggies (chives, broccoli, cauliflower, etc)
In a medium saucepan, combine cauliflower and broccoli with a little salted water and cook, covered for about 3 minutes. Remove the broccoli with a slotted spoon and set aside in a bowl, continue cooking the cauliflower until soft, about 5 more minutes. Drain and set aside in a separate large bowl.
Cut the potatoes in half lengthwise. Scoop the flesh out into the large bowl with the cauliflower, leaving a ¼" shell. Place the potato shells on a baking sheet.
Mash the flesh with a potato masher or puree with a hand blender along with the cauliflower. Add the buttermilk, sour cream, butter, pepper, and salt, mash until smooth. Fold in half of the shredded cheddar (and chives if desired).
Spoon the potato/cauliflower mixture back into the shells. Top with the cooked broccoli and remaining cheese on top.
Bake for 5-10 minutes, or until heated through and the cheese is melted.