Place potatoes in a large saucepan, cover with water, and bring to a gentle boil. Reduce heat and simmer 10 minutes. Add cauliflower. Cook for another 5–10 minutes, until everything is fork-tender. Drain and return to saucepan. Turn heat to medium and add remaining 2 teaspoons olive oil, plus broth or stock. Mash with a potato masher, adding more stock if needed to reach desired consistency. Stir in roasted garlic, onions, and chives, mashing as desired. Season to taste with salt and pepper. Remove from heat, transfer to a serving dish, and sprinkle with smoked paprika. Serve immediately.