Combine all ingredients in a small food processor or blender with 2 tablespoons of water, a pinch of salt, and freshly ground black pepper. Blend until smooth and add an additional 1 to 2 tablespoons water to thin out the dressing as desired. Dip some kale into the dressing then taste and adjust flavoring, adding more salt, pepper, or syrup as desired.
Optional Step: Heat oil in a large frying pan over medium-high heat and add the pancetta. Cook stirring frequently, until the pancetta is browned and crisp, about 5 minutes. Using a slotted spoon, remove pancetta to a paper-towel lined plate and set aside to drain.
Remove all but 1 1/2 tablespoons drippings from the pan and reserve for another use (like the dressing above). Add the lemon juice to the drippings in the pan (off heat), scrape the bottom of the pan to collect any browned bits; then pour into a large nonreactive bowl. Add the apples, kale, endive and dressing and toss to coat. Mound the salad on serving plates, garnish with the currants, pancetta, walnuts, and serve.
Note: When crisping the pancetta, reserve 1 tablespoon for the dressing if you want a smokier dressing flavor; otherwise, use olive oil. To make dicing the pancetta easier, place the pancetta in the freezer until thoroughly chilled, about 10 to 15 minutes and then use a serrated knife to cut it.