Bring a medium saucepan of salted water to the boil for the spaghetti. Finely chop the onion. Finely chop the parsley, including the stems. Finely grate the parmesan.
Step 2 — Cook spaghetti
Add three-quarters of the spaghetti* to the pan of boiling water (if you're tempted to throw in all the spaghetti, just note the dish won't be as saucy). Cook, stirring occasionally, for 12 mins or until al dente. Reserve 1½ tbs cooking water, then drain the spaghetti.
Step 3 — Fry bacon and onion
Meanwhile, heat 1 tsp olive oil in a medium deep frypan over medium-high heat. Cook the bacon and onion, stirring occasionally, for 6-8 mins until the bacon is crisp.
Step 4 — Simmer sauce
Add three-quarters of the cream* and 3 tsp pepper and garlic seasoning (reduce the seasoning for a milder pepper kick) and 60ml (¼ cup) water to the bacon mixture and bring to a gentle simmer. Reduce the heat to medium and cook, stirring occasionally, for 2-3 mins until slightly reduced. Taste, then season with salt.
Step 5 — Toss salad
While the sauce is cooking, whisk 2 tsp extra virgin olive oil and 1 tsp balsamic vinegar in a large bowl and season with salt and pepper. Add the spinach and 1 tbs parmesan to the dressing and toss to coat.
Step 6 — Get ready to serve
Add the spaghetti, reserved cooking water, half the parsley and half the remaining parmesan to the sauce and toss until the sauce coats the spaghetti. Taste, then season with salt and pepper. Divide the spaghetti among bowls and scatter with the remaining parsley and remaining parmesan. Serve with the spinach salad.