Heat a large heavy pot to medium heat with 2 tablespoons of olive oil and add the sausage. Cook the sausage until browned while breaking it up into small pieces. Once browned, remove the sausage to a plate with a slotted spoon.
Add the remaining olive oil along with the leeks, celery, carrot, fennel seeds, a pinch of salt, and a 1/4 cup of water. With a wooden spoon, scrape the bottom of the pan to dislodge the brown bits. Cook until soft while stirring every so often (about 10-15 minutes). If the veggies starts to burn, simply add a splash of water. Add the garlic and cook for another 2 minutes or until fragrant.
Next, add the wine and turn the heat to high. Again, with a wooden spoon scrape the bottom of the pot to dislodge any remaining brown bits. Once the wine has reduced by half (about 1-2 minutes) add the cooked sausage, chicken stock, and Parmesan rind. Bring to a boil.
Once boiling, lower the heat and simmer for 5 minutes. Add the cream and simmer the soup for another 10 minutes.
Add the gnocchi and cook until tender (about 2-3 minutes) then add the spinach leaves and cook for another 30 seconds. Remove the pot from the heat and taste test the soup. Adjust salt and pepper if required. Stir in the basil.
Serve in bowls with grated cheese and crusty bread. Enjoy!