Cut the chicken breasts into strips across the breast 4-5mm (¼") thick and place them in a medium bowl.
Chop the chilli peppers into a dice as finely as you can.
Peel the garlic cloves and dice them as finely as you can.
Slice the spring onions into rounds 2-3mm (⅛") thick.
Heat a wok over a high heat and add the black peppercorns and Szechuan pepper and toast them for 1-2 minutes. Then remove and grind them in a pestle and mortar or a spice grinder.
Add half of the ground pepper mix to the chicken along with the Chinese 5 spice and half of the coarse sea salt, and mix to coat.
Heat 4-5cm (1½-2") of oil in a wok or deep fat fryer to a temperature of 180°C or 350°F.
Just before the oil reaches the desired temperature, toss the cornstarch into the chicken, mix to combine and then fry in the oil (in two batches) for 60-90 seconds per batch. When fried, remove from the oil and place on kitchen paper to absorb any excess oil.
When the chicken is cooked, carefully pour out the hot oil into a separate saucepan to cool, retaining a little coating in the wok. Then return the wok to a high heat.
Throw in the garlic, chilli, and spring onions, then stir fry for 30 seconds.
Add the fried chicken and the remaining pepper mix, the remaining salt and the MSG then toss to combine everything and serve immediately.