Prep the cauliflower:
Cut 1 medium head of cauliflower into florets. Rinse and pat dry thoroughly.
Blanch the cauliflower:
Bring a large pot of salted water to a boil. Add the cauliflower florets and cook for 2–3 minutes, just until slightly tender but still firm. Drain well and pat completely dry with paper towels.
Make the batter:
In a large bowl, whisk together the flour, cornstarch, baking powder, salt, and spices. Slowly add the cold sparkling water, whisking until smooth. The batter should be thick enough to coat the florets but still drip slightly — like pancake batter.
Coat the florets:
Dip each floret into the batter, letting any excess drip off.
Fry or bake:To fry: Heat the oil to 350°F (175°C). Fry florets in batches for 3–5 minutes, or until golden and crispy. Drain on paper towels.To bake: Preheat oven to 425°F (220°C). Line a baking sheet with parchment. Place battered florets on the sheet and spray with oil. Bake for 25–30 minutes, flipping halfway, until golden and crisp.