Place all the piri-piri sauce ingredients together in the bowl of a food processor or blender; process until smooth. Reserve ½ cup of the marinade.
Try and season your spatchcocked chicken with salt. Smother marinade over chicken and refrigerate while prepping the rest of your ingredients (can leave in the marinating in the fridge up to 3 hours, take out 30 min before roasting).
Preheat oven to 400 F degrees. Cut baby potatoes in half or if using larger potatoes, cut into wedges. Toss potatoes with 2 tablespoons of olive oil, salt and pepper and roast for 20 min, shaking pan occasionally.
While the potatoes roast, cube bread and cut half the cherry tomatoes in half (optional to cut tomatoes).
When the potatoes are ready, increase oven to 450 F degrees. Add the bread cubes and ¾ of the cherry tomatoes to the pan and toss all with the reserved sauce. Either all of it or save some to serve with the chicken. Add the thyme sprigs and place the chicken on top, spreading half the butter on the chicken.
Baste the chicken every 10-20 minutes, with the pan sauce and spread the remaining butter on the chicken about halfway through roasting, add the remaining cherry tomatoes (that are cut in halat this time.
Roast for about 40-50 minutes (exact time will depend on size of chicke), until a thermometer inserted in the thickest part reaches 165 Add flaky sea salt and freshly ground pepper, garnish with extra herbs and serve with any remaining sauce on the side.