Bring a large saucepan of salted water to the boil. Finely chop garlic. Grate zucchini.

In a medium bowl, combine beef mince, fine breadcrumbs, the egg, basil pesto and a pinch of salt and pepper. Using damp hands, roll heaped spoonfuls of beef mixture into small meatballs (4-5 per person).

Cook spaghetti in the boiling water until 'al dente', 10 minutes. Reserve some pasta water (1/3 cup for 2 people / 2/3 cup for 4 people), then drain spaghetti and return to saucepan. Drizzle with olive oil to prevent sticking. While pasta is cooking, heat a drizzle of olive oil in a large frying pan over medium-high heat. Cook meatballs, gently turning, until browned and cooked through, 5-6 minutes (cook in batches if pan is getting crowded). Transfer to a plate.

Wipe out frying pan, then return to medium-high heat with another drizzle of olive oil, if needed. Cook mushrooms, garlic, dried oregano (see ingredients) and zucchini, tossing, until softened, 5-6 minutes. Stir in passata, the brown sugar, butter, beef-style stock powder and some reserved pasta water. Bring to the boil.

Once the sauce is boiling, add meatballs and grated Parmesan cheese to sauce. Cover with a lid or foil. Reduce heat to medium, then simmer until meatballs are cooked through, 6-7 minutes. Stir in baby spinach leaves until just wilted, 1 minute. Season to taste, then remove from heat.

Divide spaghetti between plates. Top with beef and basil pesto meatballs to serve.