Boil the kettle, prepare your ingredients and get your equipment ready. Read through the instructions first to familiarise yourself with the recipe as you'll need to move quickly to keep on top of the timings.
Heat the extra virgin olive oil in a large frying pan over medium-high heat. Add the bacon to the pan and fry for about 4 minutes until it starts to turn crispy. Stir every so often so that both sides cook evenly.
Meanwhile, pour the boiling kettle water into a saucepan, add the salt and cook the spaghetti until al dente (see packet instructions). This usually takes about 8 minutes.
While the spaghetti is simmering away, grab a bowl and mix 1 whole egg, 2 egg yolks, grated pecorino cheese and black pepper. Set aside.
Now, back to the bacon. It should be nice and crispy, so add the mushrooms to the pan and fry for 2 minutes.
Now, add the rosemary and garlic to the pan and fry for a further 1 minute until fragrant. Don't let the garlic burn as it will add a bitter taste to the entire dish.
You can now add the courgette (zucchini) to the pan and fry for a further 2 minutes until the courgette has softened slightly but still has a ‘spaghetti-like’ bite. You do not want this to be mushy. Now, remove the frying pan from the heat.
The spaghetti should nearly be at al dente stage. Give it a taste test. Quickly, remove 3 tablespoons of the starchy pasta water and whisk it into the egg and cheese mixture with a fork. The egg is now tempered, which will help to prevent it from scrambling as it combines with the hot pasta.
Drain the remaining water from the spaghetti and pour the spaghetti into the pan with the bacon and other ingredients. Working quickly, toss the spaghetti around in the pan to coat it with all the flavours.
Still working quickly, pour the tempered egg mixture into the frying pan, continuously tossing it through the spaghetti as you pour. This will prevent scrambling.
The residue heat from the spaghetti will cook the egg, melt the cheese, react with the starchy water you previously added to the egg mixture and produce a velvety sauce. Pour into serving bowls and top with a generous grind of pepper and serve immediately.