Roast cauliflower florets and chopped cauliflower.
In a 375°(190°C) oven, roast ½ head of chopped cauliflower for the soup and 1 cup of extra cauliflower separated into small florets for garnish. Drizzle olive oil and salt and pepper to taste. Roast for 20-30 minutes, or until cauliflower is aromatic and browned nicely. Set aside.
Boil soup ingredients.
In a pot, combine chopped celery, sliced leeks, and roughly cubed potato with chicken broth and bring to a boil over medium heat. Allow vegetables to soften over low-medium heat, about 10-15 minutes. Turn heat off and transfer mixture to a food processor. Add the roasted cauliflower from step 1 to food processor and blend until smooth. If your food processor is too small for all the ingredients, you can do this in two or three batches. Transfer the pureéd mixture back to pot and heat up over medium heat. Add heavy cream and the reserved cauliflower stems and cook until stems have softened. Salt and pepper to taste.
Make gnocchi: boil cauliflower & potatoes in salted water.
Get a pot of water to a boil over high heat and boil cauliflower and potatoes until soft. When Check by sticking a fork through the cauliflower and potato. They should be soft and almost just disintegrate when you stick the fork through. Drain and transfer to a large bowl.
Using a potato masher, mash the cauliflower and potatoes until smooth. For a more convenient way for a smooth dough, you can also blend the mixture in a food processor.
Make a well and crack egg into mashed cauliflower and potato, mix.
Lay the mashed mixture on a chopping board and make a well in the center. Crack an egg into the well, add salt, and use your hands to incorporate the egg into the cauliflower potato mix.
Combine flour and cauliflower potato mixture.
Slowly sprinkle flour onto the mixture and incorporate the four to make the dough. Using your hands, fold and push down on the dough, continuing to knead and incorporate all the ingredients well. You should end up with a smooth dough that is soft. Add more flour a little at a time if the dough is too sticky to handle.
Slice dough into four parts.
Roll the dough into a circular shape and slice it into 4 equal parts.
Roll dough out and cut.
With each 4 parts of the dough, roll them out into long logs, about ½”-¾” thick. Cut the logs ½” wide to make each gnocchi and continue cutting until the entire log is cut up.
Bring another pot of water to a boil over high heat and boil the raw gnocchi in water. Don’t forget to salt the water and add a couple dollops of olive oil! When the gnocchi floats, it is ready to remove and set aside.
Assemble, garnish & serve.
Shave some fresh cauliflower either using a mandolin or hand cut with a chef knife. Slice carefully to make sure each slice is thin, like paper. Ladle the soup into a serving bowl. Scoop the cooked gnocchi and place it in the center of the bowl. Take some of the roasted cauliflower for garnish and place over the gnocchi and soup. Lay the shaved fresh cauliflower on top. Finish with a drizzle of olive oil and a pinch of pepper. Congrats! You just made cauliflower gnocchi.