The procedure:
Preheat the oven to 250 degrees F. Place the raw walnuts in a shallow pan and roast for 30 minutes, stirring once in a while so the nuts roast evenly. Keep an eye on them so they don’t burn and turn bitter. Once it starts to get fragrant, it’s almost ready. Remove the pan from the oven and let the walnuts cool.

Meanwhile, in a large pan, pan roast the black sesame seeds over medium-low heat, stirring continuously. Roast for about 10 minutes, or until the seeds start to smell fragrant. Turn off the heat immediately and remove the pan to a cool place. Grind the seeds in a spice grinder, coffee grinder or if you have a Vita-Mix/Blendtec, until you have a wonderfully fragrant powder. Make sure to scrape down the sides periodically so that you have a uniform grind.

By the way, grinding the seeds to a powder before making the butter ensures that you have a creamy end product; trying to grind the whole seeds with the walnuts will only result in a grainy, hulled butter. If this is what you prefer, by all means go for it

Once the black sesame powder and walnuts are cooled, place them in the bowl of your food processor along with the sea salt and sugar. Grind until creamy; this should only take about 2 – 3 minutes; it will first ball up, then loosen as the walnuts release their oils. Keep going until your tahini is whipped and smooth.

Scrape into a sterilized glass jar; allow to cool (it will be a bit warm from the processing) before putting on the cap and storing in the refrigerator. I’ll wager it’ll keep for at least two weeks, but keep an eye on it as walnut oils tend to go rancid quite easily.