This recipe is quick to put together but takes a couple of hours to make. The flavor only improves overnight as well, which makes it a great meal to make ahead and bring to a party or event.
Slice the roast into 25 mm thick planks. Combine the remaining ingredients, except the giardiniera, in a large casserole dish. Stir to combine. Place the planks of rump roast in the casserole dish, trying not to overlap if possible. Place the casserole dish in the steam oven on the wire rack and set at position 2. Turn the steam oven on by selecting the Convection Steam Mode set to 135°C. Set the timer for 1 hour and 45 minutes. After the timer goes off, pull the casserole dish out of the steam oven and place on a heatproof surface. Flip the pieces of meat over and add the jar of giardiniera along with 130 mL of water. Return the casserole dish to the oven and set the time for 45 minutes. After the timer goes off, remove the casserole dish and add the remaining 350 mL of water. Pull the beef apart with forks or a set of tongs. Serve on its own or in sandwiches.