Rinse the corned silverside in cold water to remove any surface brine. Place the corned silverside in a large heavy based pot, large enough for the meat to be completely submersed in water. Cover the silverside with cold water.
Place over a low heat and bring to just a simmer. Skim any scum that rises to the surface. Once all scum is removed, add onion, peppercorns, golden syrup and mustard. Tear mandarins into quarters, squeeze juice into cooking liquid, then add mandarin quarters.
Keep the heat at simmering point, small bubbles will occasionally rise to the surface. Adjust the heat throughout the cooking time. Cook until the silverside is tender. A fork should easily penetrate the centre of the meat.
Meanwhile, cook cauliflower in a saucepan of boiling water for 8 minutes, or until tender. Drain. Place in a food processor with the olive oil and Parmesan and process until smooth. Season to taste with sea salt.
Meanwhile, place 180ml (¾ cup) of the cooking liquid in a saucepan with the extra golden syrup and mustard. Simmer over a medium heat for 4 minutes or until reduced by half and syrupy.
Slice silverside against the grain. Serve on the cauliflower mash with steamed greens, drizzled with the mustard sauce.
Tips
For potato cauliflower mash - you can replace half the cauliflower with peeled and chopped potato (500g), but will need to cook for 10-12 minutes, or until tender.
You can swap the olive oil and Parmesan in the mash with 2 tbsp sour cream.
