For the short rib dry cure mix: Mix together the sea salt, celery salt, coriander, garlic powder, ginger, Herbes de Provence, paprika, black pepper and chile powder in a small bowl. Rub them into the beef. Place the beef in a large pan or container, cover and refrigerate overnight or up to 24 hours.
For the BBQ glaze: Roughly chop the pickled onions and dates and place them in a bowl. Heat the stout in a small saucepan until boiling. Pour it over the onions and dates, cover with plastic wrap and let cool to room temperature.
In a separate large bowl, whisk together the apple juice, golden syrup, honey, mustard, brown sugar, black treacle, Worcester sauce, hot sauce and tomato paste.
When the date and onion mix has cooled and the dates have softened, add the mix to a blender and puree until smooth. Add it to the apple juice mixture and stir to combine.
Preheat the oven to 275 degrees F. Wash the dry cure mix off the beef and place in a large flameproof casserole or roasting pan with a lid (Alternatively, use foil to cover the pan). Pour over the glaze, cover, and roast until the beef is very tender, 5 to 6 hours. Make sure the glaze doesn't evaporate completely; if it is reducing down too much, add some water to the pan.
Let the beef cool to room temperature, then chill overnight in the refrigerator. When cold the fat will set on the top and can be easily removed.
When ready to reheat, heat a grill to low. Place the covered pan on the grill and cook to warm through, 2 to 3 hours.
When warm, remove the lid and slowly reduce the glaze with the beef still in the pan, basting the ribs every 10 minutes. When the glaze is reduced and coats the beef, remove the ribs from the pan and serve.
Golden syrup (also called pale treacle) and black treacle are sweet byproducts of the sugar refining process and are popular in British cooking. You can find them at some specialty food stores and online markets.