Heat a drizzle of olive oil in a large non-stick frying pan with fairly deep sides. Remove the sausages from their skins and add to the pan, using the back of a wooden spoon to crumble them up (you want the texture to be a bit like mince). Cook over a high heat for about 5-10 minutes, stirring occasionally, or until crispy and golden on all sides. Tip into a bowl and set aside.
In the same pan, over a low heat, add the butter and swirl until melted. Add the onion and season with salt and freshly ground black pepper. Sauté over a low heat, stirring occasionally, for about 5-7 minutes - or until the onions are lovely and soft.. Add the garlic and cook for a further minute or so, stirring to ensure it doesn’t catch and burn (or it will become bitter).
Pour in the vodka and mix well. Allow almost all of it to bubble off before adding the tomato purée and chilli paste. Stir well to coat the onions before pouring in the chopped tomatoes and balsamic vinegar. Rinse out the can of tomatoes with about 100 ml of water, then bring to a simmer. Simmer for about 5-10 minutes, or until slightly thickened and reduced.
Meanwhile, cook the rigatoni in a pan of boiling salted water according to packet instructions - or until al dente. Reserve a little of the pasta water and drain well.
At this point, make the pistachio pesto (if using): add the pistachios, basil, olive oil, garlic and Parmesan to a blender and blitz until smooth. Season to taste with lemon zest and juice and salt and freshly ground black pepper. I suggest doing this gradually - you can always add more lemon and seasoning, but you can’t take it away. Also bear in mind that Parmesan is quite salty. Spoon into a bowl, cover and set aside. Alternatively, spoon into an airtight container and chill for up to 7 days.
Remove from the sauce from the heat and blend until smooth - you can use a handheld stick blender or tip into a food processor. Take care as it will be hot (you might like to let it cool for about 5 minutes or so). If using a food processor, return to the pan.
Stir in the double cream and bring back to a simmer. Return the crispy sausages to the pan and add the drained pasta and grated Parmesan. Mix well to coat everything in the deliciously creamy vodka tomato sauce. Season to taste. Stir in a splash of the reserved pasta water if it is a little too thick.
To serve: spoon onto plates and drizzle generously with the pistachio pesto (or any other fresh pesto). Top with torn burrata and a little more freshly grated Parmesan. Season with freshly ground black pepper and serve.