1 Boil, steam or microwave the sweet potato until tender. Drain.
2 Meanwhile, place cauliflower in a food processor. Pulse until finely chopped. Boil, steam or microwave the cauliflower until tender. Drain and cover.
3 Combine flour and paprika in a bowl. Add beef and toss to coat, shaking off excess flour. Reserve any of the leftover flour mixture. Heat olive oil in a big deep frying pan over a medium-high heat. Cook the beef strips, stirring, for 2–3 minutes, or until browned. Transfer to a plate.
4 Reheat the same frying pan over medium-high heat. Cook onion and mushrooms, stirring, for 3–4 minutes, or until softened. Add garlic, tomato paste, mustard and reserved flour mixture. Cook, stirring, for 1 minute, or until mixture is fragrant. Add stock and sweet potato, bring to the boil. Simmer for 2–3 minutes, or until thickened.
5 Add beef, any juices and sour cream to pan. Stir to combine. Simmer for 2 minutes. Season generously with cracked black pepper. Serve stroganoff over cauliflower rice with steamed green beans.