For the slaw, whisk up dressing in a large bowl, add cabbage and toss to coat. Chill until ready to serve.
For the sauce, heat a skillet over medium heat, melt butter and add onions, garlic, salt and pepper. Soften 6-7 minutes then add chipotle purée and tomato paste. Stir a minute and add stock, Worcestershire, Tamari and sugar. Bring to a bubble then reduce to low simmer.