Preheat the oven to 400 F/ 200C and mince the garlic and ginger. To make the sauce, in a small saucepan, heat soy sauce, sweet chili sauce, golden syrup, garlic, and ginger on medium heat and bring to a boil. Turn down the heat and allow the sauce to simmer, whisking occasionally, until the sauce is thick and bubbly. Remove from heat.
Roughly chop the bell pepper and broccoli into florets. Spread chicken and chopped veggies on a baking sheet sprayed with cooking spray and season with salt and pepper. Drizzle half the sauce over the chicken and veggies (reserving the other half for later) and toss to combine.
Bake in the oven for about 20 minutes, tossing halfway through, and continue cooking until veggies are tender and chicken is cooked through.
Thinly slice the green onions. Drizzle the remaining sauce over the top and sprinkle with sesame seeds and green onions. Serve immediately and enjoy!