In a large mixing bowl, add all of the ingredients for the marinade and mix together until well-combined. Use a whisk of the mustard remains a little 'bitty'!
Remove around a third of the mixture and transfer to a small bowl - cover and place into the fridge for later.
Add all of your chopped chicken breast chunks to the remaining marinade and mix until well-coated. Cover with clingfilm and place in the fridge for anywhere from 30 minutes to overnight.
Once marinated, chop your courgette into 1cm thick discs and slice your red pepper into squares.
Grab your skewers and thread on a piece of courgette or red pepper, then chicken, then alternating veg and chicken until the skewer is full. Repeat until you've used up all your chicken chunks.
If BBQ'ing, once heated, place onto the rack and turn every 4-5 minutes. Once nicely browned on all sides, brush the extra marinade onto the chicken chunks and BBQ until cooked through.
If grilling in the oven, preheat your grill to a medium-high heat. Place the skewers onto a grill pan rack and place under the grill for 10 minutes, then turn and cook for another 10 minutes. 5 minutes before they're done, brush the extra marinade onto the chicken chunks and grill until cooked through.
Plate up and scatter the chopped spring onion on top. Enjoy!