Bring a medium saucepan of salted water to the boil. Peel the potato and cut into 2cm chunks. Trim the green beans. Roughly chop the silverbeet. Finely chop the garlic (or use a garlic press). Crush the black peppercorns (see ingredients list) in a pestle and mortar, or in their sachet using a rolling pin. Place your hand flat on top of each chicken breast and slice horizontally, without cutting all the way through. Open up each chicken breast like a book.

Add the potato to the saucepan of boiling water and cook until easily pierced with a knife, 10-15 minutes. Drain the potato and return to the saucepan. Add the salt, milk and 1/2 the butter and mash using a potato masher or fork until smooth. Cover to keep warm.

While the potato is cooking, heat a large frying pan over a medium-high heat. Add the walnuts and toast until golden, 3-4 minutes. Transfer to a plate. Return the pan to a medium-high heat with 1/2 the butter and a drizzle of olive oil. Add the green beans and silverbeet and cook until just tender, 4-5 minutes. Add 1/2 the garlic and cook until fragrant, 30 seconds. Season to taste and transfer to a bowl. Cover to keep warm. TIP: Add a splash of water to help the veggies cook faster.

Return the pan to a medium-high heat with a drizzle of olive oil. Season the butterflied chicken on both sides with salt, then add to the pan. Cook until cooked through, 2-4 minutes each side. Transfer to a plate to rest. TIP: The chicken is cooked through when it's no longer pink inside.

Return the pan to a medium heat with a drizzle of olive oil. Add the crushed peppercorns and remaining garlic and cook for 30 seconds or until fragrant. Reduce the heat to low, add a dash of water and scrape up any bits stuck to the bottom of the pan. Add the light cooking cream and crumble in the chicken stock (1/2 cube for 2 people / 1 cube for 4 people). Cook, stirring, until thickened, 2-3 minutes. Add any chicken resting juices and season to taste with salt and pepper.

Toss the walnuts through the greens. Divide the potato mash, chicken and greens between plates. Spoon the creamy peppercorn sauce over the chicken to serve.