Preheat the oven to 300 F and heat the SousVide Supreme to 125 F.
Combine the 2 tablespoons of table salt or 4 tablespoons of Diamond crystal kosher salt with 1 cup of water in a measuring cup to make a 10% brine.
Divide the large black cod fillets into two portions for 3 fillets total.
Carefully remove the skins from each piece and season the skins with salt on both sides.
Place the skins on a parchment-lined baking sheet. Throw them into the oven for 35 minutes.
While the skins are cooking, grab a pair of clean tweezers and remove the pine bones from the fillets.
Put the fillets in a bag and pour in the brine. Let them sit in a bowl of ice in the fridge for 10 minutes. (You don’t have to brine the fillets but it helps with the flavor AND you won’t get the unsightly white albumin all over the finished product.)
After brining, remove the fillets from the bag, rinse them in the sink, and dry them with paper towels.
Vacuum seal each fillet with a pat of ghee or butter and a sprig of thyme.
Dunk the sealed fillets in the water oven for 20 minutes.
The skins should be finishing up in the oven. When they are done, remove them from the pan to a wire rack to cool.
When the fillets are finished cooking, put them on a platter and top with the reserved cooking liquid/melted butter.
Top the fillets with pepper, fleur de sel, and a squeeze of fresh lemon juice.