Before you start, bring a large pot of salted water to the boil.
Prep kumara and carrot and cook in pot of boiling water for 15-20 minutes, until tender. Drain, return to pot with first measure of butter and milk and mash until smooth.
Prep broccoli, mushrooms and garlic.
Pat beef dry and season with crushed pink and green peppercorns and salt. Heat oil in a large fry-pan on a medium heat.
Cook beef for about 3 minutes each side for medium, depending on thickness, or until cooked to your liking. Rest, covered and reserve pan.
Wipe pan clean and return to high heat with oil. Stir-fry broccoli and mushrooms for about 3 minutes, until just tender. Add garlic and second measure of butter and cook for 1 minute, until fragrant. Season to taste with salt and pepper.
To finish, thinly slice beef against the grain.
Serve mash, beef and veggies with hollandaise sauce.