While most marrow bones are cut crosswise, they can be ordered cut lengthwise from any quality butcher.
Ingredients: 2-4 ppl
Two (7 to 8-inch/17.5 to 20-cm) centre-cut veal marrow bones, cut in half lengthwise to make 4 pieces total
1/2 cup (125 mL) chopped flat-leaf parsley
1 each: shallot, clove garlic (both finely chopped)
1-1/2 tbsp (22 mL) capers, rinsed, dried, finely chopped
1 tbsp (15 mL) white vinegar
1-1/2 tsp (7 mL) each: red wine vinegar, granulated sugar
1/4 cup (60 mL) extra-virgin olive oil
1/2 baguette, thinly sliced
Coarse sea salt for serving, preferably Maldon
Place bones in large container. Using measuring cup, pour in cold water to cover. For every 1 cup (250 mL) water, add 1 tsp (5 mL) salt. Refrigerate 24 hours, changing water and salt 3 to 4 times. Drain, pat dry with paper towel and let stand at room temperature for 1 hour.
To make chimichurri, combine parsley, shallot, garlic, capers, white vinegar, red wine vinegar, sugar and oil in small bowl. Season with kosher salt to taste.
Preheat oven to 450F (230C). Place bones in roasting pan, marrow side up. Roast on middle rack until tip of paring knife inserted in thickest part of marrow feels hot to the touch, 8 to 10 minutes. (Be careful to not overcook, or marrow will melt away.) While bones are roasting, place baguette slices on baking tray and bake on upper rack until toasted, 3 to 4 minutes. Serve marrow hot with toasts, coarse salt and chimichurri. To eat, scoop marrow onto toasts, sprinkle salt and spread with chimichurri.