Trim the leeks just above the white part of the stalk. Wash the top greens, and put them in a pot with a pinch of sea salt, the chicken stock, and 2 cups water.
Simmer for 30 minutes, then remove and discard the leek greens.
Wash and thinly slice the white part of the leeks, and add to a deep sauté pan (or small stock pot or Dutch oven) with the olive oil.
Cook over low heat until the leeks are translucent, 3-4 minutes.
Add the sausage, and cook, stirring occasionally, for 3-4 minutes, until browned on all sides.
Add red pepper flakes, white wine, and fregula. Stir to combine, and add the hot chicken stock.
Bring to a boil over medium heat; then reduce heat to low and simmer until the fregula is cooked through and most of the liquid is absorbed (add additional water, a few Tbsp at a time, if needed).
Remove from heat, and stir in the cheese, parsley, and plenty of black pepper. Serve hot or at room temperature.