Heat neutral oil in a large skillet or wok over medium-high heat until shimmering and hot.

Fry the chicken in batches until golden brown and crispy on the outside while remaining juicy inside, then transfer to a paper towel-lined plate.

Carefully drain excess oil from the skillet, leaving about 2 tablespoons behind for stir frying.

Add sesame oil to the pan and sauté the sliced onion until slightly softened and fragrant.

Stir in the bell peppers and cook until tender-crisp with lightly charred edges.

Add diced mangoes and cook briefly so they soften slightly but still hold their shape.

In a small bowl, whisk together soy sauce, sweet chili sauce, rice vinegar, honey, chili garlic sauce, and water until smooth.

Pour the sauce into the skillet and simmer for a few minutes until glossy and aromatic.

Stir the cornstarch slurry into the sauce and cook until slightly thickened and silky.

Return the crispy chicken to the pan and toss gently until every piece is coated in the sticky mango sauce.

Sprinkle with green onions and sesame seeds before serving hot over rice or noodles.