Wash and peel the potatoes (peeling optional). Cut into 1/2-inch thick sticks (matchstick or thick fry style). Immediately place cut potatoes in a bowl of cold water and soak for 20–30 minutes to remove excess starch.

Dry and season

Drain the potatoes and pat them thoroughly dry with kitchen towels — very important for crispiness. In a large bowl, combine cornstarch, all-purpose flour, salt, and black pepper. Add about 1/2 cup water gradually and whisk to make a slightly thick batter that will coat the fries; adjust so it clings but is not runny.

Coat potatoes

Toss the dried potato sticks in the batter to coat them evenly. Shake off excess batter so each piece has a thin coating.

Fry potatoes

Heat vegetable oil in a deep heavy-bottomed pot or deep fryer to 325°F (160–165°C) for the first fry. Fry potatoes in batches (do not overcrowd) for 4–5 minutes until pale golden and cooked through but not deeply browned. Remove and drain on a wire rack. Increase oil temperature to 375°F (190–195°C) and fry the potatoes a second time in batches for 2–3 minutes until golden brown and very crisp. Drain on paper towels or a rack and lightly season with a pinch of salt while hot.

Sauce and aromatics

Mix sauce

In a small bowl combine honey, sriracha (or sweet chili sauce), ketchup, soy sauce, rice vinegar, 2 tablespoons water, and sesame oil. Whisk until smooth. In a separate teaspoon-sized bowl stir 1 teaspoon cornstarch with 1 teaspoon cold water to make a slurry; set aside.

Aromatics

Heat 2 tablespoons neutral oil in a large wide skillet or wok over medium-high heat. Add the white parts of the sliced spring onions, minced garlic, minced ginger, and sliced green chili. Stir-fry for 20–30 seconds until fragrant but not browned. If using diced red bell pepper, add it now and stir-fry 30–45 seconds to soften slightly.

Finish sauce

Pour the prepared honey-chilli sauce mixture into the skillet with the aromatics. Bring to a gentle simmer for about 30 seconds. Stir the cornstarch slurry again and drizzle into the simmering sauce while stirring — this will thicken the sauce within 10–20 seconds to a glossy, clingy consistency. Taste and adjust: add a pinch of salt, more honey for sweetness, or more sriracha for heat as desired.

Combine potatoes and sauce

Reduce heat to low. Add the double-fried crispy potatoes to the skillet and toss quickly but gently so each piece is evenly coated with the sauce — do this in two quick batches if necessary to avoid sogginess. Toss for 20–30 seconds just to coat; do not simmer the potatoes in sauce for long or they will soften.

Finish

Turn off heat and sprinkle the green parts of the spring onions and toasted sesame seeds over the coated potatoes. Give a final gentle toss. Drizzle the 1/2 teaspoon of sesame oil over the top for aroma and toss once more.

Serving

Transfer the honey chilli potatoes to a serving platter and serve immediately while hot and crisp. Offer extra sliced green onions and a wedge of lemon on the side if desired.