Pour the flour into a shallow dish and season well with salt and pepper. Dust the chicken in the seasoned flour. If some of the chicken breasts you get are on the thick side then place them between 2 pieces of greaseproof paper and use a rolling pin to tap them out thinner. *See notes
Heat the olive oil and butter in the pan over medium heat. Brown the chicken on both sides. Don't worry if the chicken isn't cooked all the way through. It gets added back to the pan to finish cooking in the sauce. Once the chicken is brown on both sides, this should only take about 6-10 minutes, remove the chicken from the pan to a plate and set it aside while you make the sauce. Leave any of the brown bits of chicken that have stuck to the pan.
Add the onion and sweet corn to the pan and let cook until the onions are soft and translucent. As the onions soften, use a spoon to scrape the brown bits off the bottom of the pan. Add the pepper slices and tomato paste to the pan and continue to cook for another 5-8 minutes.
Pour the cream and chicken stock into the pan and add the spice mix. Squeeze in the lemon juice and adjust the seasoning. Bring it to a simmer and add the chicken back to the pan. Let gently cook for about 10 minutes until the chicken is cooked and the sauce has thickened.
Add in the spinach and let wilt in the hot sauce. Garnish the top of the chicken with some diced red onion, sliced green onion and fresh coriander and basil.