Heat a heavy-bottomed pan over medium heat for 2-3 minutes. Add vegetable oil and make sure it’s shimmery, then sprinkle RawSpiceBar’s Horseradish & Mustard Seeds across the surface and cover immediately, cook until seeds stop popping, about 1 minute.
Remove cover, turn heat to medium-low and add diced cabbage and onion. Add butter and salt, toss to combine, stirring until vegetables begin to wilt, about 4-5 minutes.
Turn heat to medium-low and cover the pan. Cook for 10-12 minutes, until the cabbage is tender. Remove from heat.