Prepare Chicken Pieces: Add diced chicken, 1 tablespoon each of lemongrass paste, crushed garlic, grated ginger and curry powder to a large bowl. Mix together until chicken is thoroughly coated.
Cook Chicken and set Aside: Heat a non stick wok or skillet on medium to high heat. Cook chicken pieces for a few minutes until cooked through and then remove from wok, cover and set aside.
Add Aromatics: In the same skillet, add the 2 tablespoons Vegetable oil, diced onion, 1 tablespoon crushed garlic, 1 teaspoon grated ginger, 1 teaspoon lemongrass paste, 1 tablespoon curry powder, and 1 tablespoon yellow curry paste and stir through until it becomes fragrant.
Add Vegetables: Add diced bell peppers/capsicums, zucchini, and pumpkin (or any other vegetable you're using) and stir through the curry paste until coated.
Add Remaining Ingredients: Add Coconut milk, fish sauce, lime juice, sweetener and lime leaves and stir through, letting it come to a gentle bubble on medium to high heat (about 3 – 4 minutes)
Return Chicken to Pan: Add chicken pieces back into the curry, stirring though to combine everything together. Reduce heat to medium for 1 minute.
Optional Thickening of Sauce: Mix together cornflour/cornstarch with water in a small jug. Pour into curry and stir through whilst still on the heat. It should thicken quickly in under 1 minute.
Serving: Divide amongst bowls, adding rice first, and curry on top. Garnish with lime wedge and sprigs or coriander/cilantro.