Blanch the spinach for 10-15 seconds and quickly shock them in Ice bath to stop the cooking. This will also help preserve the green color. Gently squeeze the water out of the leaves.

Heat a heavy bottom pan and add the olive oil. Add garlic, leeks, shallots, and lemon zest. Sauce for 5 minutes on medium low until shallots and leeks are translucent. 

Add squeezed spinach, and all the spices and herbs. Sauce for 3-5 minutes. Transfer the cooked spinach, basil leaves, parmesan cheese, nuts and milk in a high powered blender and blend to a smooth puree.

Transfer the puree back into the pan, add the cream and boil over low heat for 2 minutes. Check for seasoning. 

This sauce could be frozen for later used. If it gets too thick, then add little bit milk or heavy cream to get the saucy consistency.

Put the broccoli florets in a food processor and blend for few seconds until its coarsely blended.

Transfer it to a mixing bowl and add rest of the ingredients. Mix well and check for seasoning.

Boil a pot of water and generously salt it. Add the pasta and boil it according to the package instructions.

Strain the water and fill the shells with broccoli filling.

These shells can be frozen for later use. To freeze them, lay them on a sheet pan in a single layer and put in freezer for few house or until completely frozen. Transfer in a ziplock bag and store in freezer.

To cook them, preheat the oven at 350 degrees. Slightly oil the oven proof serving pasta dish. Put the spinach sauce in the pan. Arrange the filled shells in a single layer with filled side at the top. Sprinkle some freshly grated parmesan cheese and drizzle little bit of olive oil. The oil will prevent the pasta from drying in the oven. Cover the top with aluminum foil and make 1-2 slits for the steam. Bake in the oven for 15-20 minutes until its hot. 

Sprinkle some parmesan cheese and some roasted nuts before serving. Serve it immediately.