In a large bowl add the cubed sweet potato, a drizzle of oil (2.5ml), 1 teaspoon dried tarragon and 1 teaspoon dried oregano. Toss together and mix well before transferring to a baking tray. Spread out well and place in the oven for 20 minutes.
Whilst the potatoes are baking make the dressing: Place all dressing ingredients into a small jug and whisk together well. Transfer to a small serving bowl and set to one side.
Next put a drizzle (2.5ml) of oil in the griddle pan, place on a high heat and then add the cubed chicken. The chicken will cook very quickly in the griddle pan so keep an eye on it and stir regularly. As the chicken starts to brown, move it to one side of the pan and add the cabbage and broccoli to the other side. Again the veggies will cook very quickly and should become slightly charred. Continue stirring until everything is cooked and charred.
After 20 minutes in the oven, remove the sweet potato and pile into a serving bowl. Next to this place the charred cabbage and broccoli and finish by topping with the chicken. Pour over the dressing and enjoy.