Prepare the cauliflower by removing the leaves and core, then cutting it into large florets, each roughly palm-sized. Rinse well and shake off excess moisture.
To make the batter, whisk together potato starch, cake flour, baking soda, salt, and white pepper in a large mixing bowl. Add water and sesame oil, whisking until smooth and lump-free. The batter should be thick enough to coat the cauliflower evenly without dripping excessively.
For the first fry, heat 4–5 cups of oil in a deep, heavy-bottomed pot to 325°F (163°C). Ensure the oil fills the pot no more than halfway to prevent overflow during frying. Dip a few cauliflower florets into the batter at a time, turning them to coat completely. Carefully lower each piece into the hot oil, frying 3–4 pieces per batch. Fry for about 2–3 minutes, until the coating turns pale golden and lightly crisp. Adjust the heat if the batter browns too quickly.
Once fried, remove the pieces using a slotted spoon and transfer them to a cooling rack set over a baking sheet. Between batches, skim any leftover crumbs from the oil to maintain its clarity. Allow the fried cauliflower to rest — this helps release steam, which will contribute to a crisper texture during the second fry.
To make the glaze, heat 2 tablespoons of oil in a saucepan over medium-low heat. Add minced shallot, garlic, and dried chili peppers (if using). Sauté for 3–4 minutes, stirring occasionally, until the shallots become translucent and the garlic is fragrant. For extra spice, chop the peppers and include their seeds; for a milder sauce, remove the seeds or omit the peppers entirely.
Add soy sauce, water, mirin, rice vinegar, brown sugar, gochujang, and Dijon mustard to the saucepan. Stir well and bring to a gentle simmer. Let the sauce cook for 4–5 minutes, stirring constantly until it thickens slightly and develops a glossy texture. Remove from heat, cover, and keep warm.
For the second fry, reheat the oil to 325°F (163°C). Fry the cauliflower once again in small batches for 1–2 minutes, until each piece is deeply golden and crisp. Drain on a cooling rack to remove excess oil.
Transfer the twice-fried cauliflower to a large mixing bowl. Pour the warm soy garlic glaze over the top and toss thoroughly until every floret is coated in the sticky, aromatic sauce. Serve immediately while hot, with a sprinkle of sesame seeds or scallions if desired. Each bite delivers a perfect balance of crunch, sweetness, spice, and savory depth.