Fill a large pot with water, bring it to a rolling boil and add some salt.
Cut the base off the head of kale and roughly tear the leaves into 2" pieces.
Place the garlic in a mortar and pestle with a heavy pinch of kosher salt and mash until liquid.
Cut the raw sausage into ½ inch chunks.
Add a little oil to the bottom of a large pot and sauté the sausage on medium until fully cooked.
Pour off grease as necessary and remove the sausage.
Drop all the kale into the boiling salted water until it turns bright green, then drain and cool in ice water.
Add the finely diced onions to the pot and sauté until soft and browned.
Add the garlic and continue stirring until fragrant.
Add ground red pepper and mix.
Deglaze the pot with a small amount of water.
Add the rest of the water, chicken stock, potatoes, and sausage.
Bring to a slow simmer until the potatoes are soft.
Add the kale and turn off the heat.
Immediately before serving, add the half and half.
