Heat up a deep skillet and add butter and 1 tablespoon of olive oil. Then add chopped onions and cook until translucent, for 2-3 minutes. Then add garlic and dry oregano and cook for another minute;
Add vodka and let it cook for about 5 minutes until almost all vodka has evaporated;
Add tomatoes, a pinch of salt and pepper, cover and cook for 10 minutes;
In a separate skillet, heat up 1 tablespoon of olive oil. Remove sausage from casing and add to the frying pan. Break the sausage with a wooden spoon and cook until fully cooked and some pieces are crispy on the edges;
In the meantime, bring a pot of salted water to boil and cook pasta according to instructions;
Once your tomatoes are cooked, transfer them to a blender and blend until smooth. You may need to do this in a few batches. (Caution: don't fill your blender with the sauce more than a third of the way up your blender because you don't want to burn yourself);
Once your sauce is blended, return it to the pan, add cream, mix well and cook for another 2-3 minutes. Then turn off the heat and add shredded Parmesan cheese, check for seasoning and adjust with salt and pepper;
Put everything together: add sausage and pasta to the sauce and mix well (you may want to leave a little bit off sausage to place on top for garnish). Either serve from a pan directly or transfer the whole dish into a serving plate, garnish with some more sausage and parsley. Enjoy!