Using a large, heavy-based saucepan, sweat the onion in the olive oil and butter over medium-low heat until translucent.

Begin with the lid off until fragrant, then pop on the lid for about 5-8 minutes, giving the onion the odd stir, then finish with the lid off again.

Meanwhile, cook spaghetti to packet instructions in well-salted boiling water.

Push the onion mixture to the side and carefully arrange the patties in the base of the pan, using a wooden spoon or potato masher to gently press them as thin as possible.

Scoop the onion mixture on top to stop it burning, crank the heat to medium-high and leave for 2-3 minutes, until the bottoms of the patties are browned.

Squash the patties into chunks and incorporate the onion mixture.

Stir the garlic through, then the tomato paste and pinch of sugar until everything is a deep shade of red, cooking for about 1-2 minutes to help cook out the rawness in the paste.

Pour in the balsamic vinegar, sniffing until the sting in your nostrils dissipates.

Pour in the stock and allow it to bubble away a little and loosen off the sauce. Keep it burbling until the sauce reduces again.

Meanwhile, put the zucchini noodles into a colander in the sink.

Reserve a mugful of pasta water then, when the pasta is ready, pour the pasta and remaining water through the zucchini in the colander to 'cook' it.

Toss about in the colander to distribute the zucchini and spaghetti evenly.

Add the zucchini and spaghetti to the pan, along with half the reserved pasta water, tossing about to incorporate.

Add more pasta water if you prefer a looser finish.

Season to taste, sprinkle with the parmesan and cracked black pepper and serve.