Prepare the Dough:

Mix warm water, sugar, and yeast in a bowl. Let it sit until frothy, about 5-10 minutes.
In a large bowl, combine flour and salt. Add the yeast mixture and olive oil, and mix to form a dough.
Knead the dough on a floured surface until smooth, about 10 minutes. Place in an oiled bowl, cover, and let it rise for 1-2 hours, until doubled.

Preheat the Oven:

Place a pizza stone or inverted baking sheet in the oven. Preheat to 500°F (260°C) for at least 30 minutes.

Prepare the Toppings:

In a large pan, heat olive oil over medium heat. Add garlic and sauté until fragrant.
Add the sausage, breaking it into pieces, and cook until browned.
Add the chopped friarielli, season with salt, pepper, and chili flakes (if using), and sauté until the greens are tender and the sausage is cooked through.

Assemble the Pizza:

Stretch the dough into a 12-inch circle on a floured surface or parchment paper.
Distribute the mozzarella evenly over the dough. Top with the sausage and friarielli mixture.

Bake the Pizza:

Transfer the pizza (on parchment if using) to the preheated stone or sheet. Bake for 10-12 minutes, until the crust is golden and cheese is bubbly.
Serve

Serve:

Remove the pizza from the oven, let it cool for a few minutes, then slice and serve.