Begin by cooking the penne pasta in a large pot of boiling salted water until al dente, following package instructions. Drain and set aside, reserving a cup of pasta water.
In a large frying pan, heat olive oil over medium heat. Add chopped onion and sauté for about 5 minutes until soft and translucent. Add minced garlic and sauté for an additional minute until fragrant.
Add the cherry tomatoes to the pan and cook for 5-7 minutes until they start to blister and soften. Stir in the double cream and bring the mixture to a gentle simmer.
Add the prawns to the pan and cook for 3-4 minutes until they turn pink and opaque. Season with salt, pepper, and a pinch of chili flakes for heat.
Reduce the heat to low, add the cooked pasta to the pan along with a splash of reserved pasta water to loosen the sauce. Stir in the baby spinach and allow it to wilt.
Finish the dish by stirring in grated Parmesan cheese and fresh basil leaves. Serve immediately, garnished with extra Parmesan and basil if desired.
