Pat steak cubes dry with a paper towel. In a bowl, toss with Cajun seasoning. Set aside while you prepare the mash.
Make the Sweet Potato Mash
Boil sweet potato in salted water for 15–18 minutes or until tender. Drain well and mash with butter, milk, salt, and pepper until smooth. Add a touch of maple syrup or honey for a subtle sweetness. Keep warm.
Cook the Greens
Blanch broccolini in boiling water for 2 minutes, then drain. Heat olive oil in a pan, sauté the garlic until fragrant, then toss in the greens. Finish with lemon juice and a pinch of salt.
Sear the Steak Bites
Heat a large pan over high heat until just smoking. Add steak in batches and sear for 2–3 minutes until golden and slightly charred. Add butter at the end to glaze and toss. Remove from the pan and rest for 5 minutes.
Optional Pan Sauce (for extra flavour)
Deglaze the pan with beef stock, Dijon, and Worcestershire. Simmer for 1–2 minutes, whisk in butter until glossy. Spoon over steak when serving or portioning.
Assemble or Portion
Add a scoop of mash to each container. Top with steak bites and garlic greens. Drizzle with the sauce, if using, and garnish with parsley.