Heat your oven to 200°C/Fan 180°C/Gas 6. Scrub the potatoes and chop them into bite-size chunks. Scatter into a roasting tin and toss with 1 tbsp oil and a generous pinch of salt and pepper. Slide into the oven and roast for 20 mins.
While the potatoes roast, peel the onions and cut into quarters. Trim the stalk off the broccoli and slice the broccoli into florets. Pick the rosemary leaves off their stalks and finely chop them. Peel and thinly slice the garlic clove.
When the potatoes have roasted for 20 mins, remove the tin from the oven and tuck in the onions and broccoli. Scatter over the garlic and rosemary and turn everything over once or twice to coat. Return to the oven for a further 20 mins.
Pour 1 tbsp oil into a large frying pan, warm to a medium-high heat. Sprinkle the chicken mini fillets with a pinch of salt and pepper and add them to the pan. Fry for 6-8 mins on each side, till they’re golden and cooked through. There should be no pink if you slice into them.
While the chicken fillets cook, finely grate the parmesan and set to one side.
When the chicken fillets are ready, transfer them to a warm plate or board and cover with foil to keep warm.
Reduce the heat under the pan to medium. Tip in the spinach and pour in 2 tbsp cold water. Cook for 1-2 mins, stirring frequently, till the leaves are wilted. Pour in half the tub of double cream (see our tip for using up the remaining half) and add the parmesan. Sprinkle in a good pinch of pepper. Cook for 2 mins, till the sauce is warmed through and slightly thickened.
Add the chicken breast mini fillets back into the pan and warm through for 1 min.
Spoon the warm chicken onto plates and pour over the creamy parmesan and spinach sauce. Serve with the roast veg on the side.