Prepare the Eggs and Cheese: In a large mixing bowl, whisk together the three egg yolks and one whole egg until they are well combined and a uniform pale yellow. Stir in the finely grated Pecorino Romano and Parmesan cheeses, along with a generous amount of freshly ground black pepper. The mixture should be thick and slightly pasty; set this aside.

Cook the Spaghetti: Bring a large pot of generously salted water to a rolling boil. Add the spaghetti, stirring occasionally to prevent sticking. Cook according to package instructions until al dente – this typically takes around 8-10 minutes. The strands should feel firm with a slight bite when tasted, but not hard. Before draining, reserve about 250ml of the starchy pasta water.

Render the Rashers: While the pasta cooks, heat two tablespoons of olive oil in a large frying pan over medium heat. Add the finely diced smoked turkey (or beef) rashers. Cook, stirring occasionally, until the rashers are deeply golden brown and crisp, releasing a wonderful savoury aroma, usually around 5-7 minutes. Once crisp, remove the rashers from the pan with a slotted spoon and place them on a plate lined with kitchen paper to drain excess fat. Leave a tablespoon or two of the rendered fat in the pan.

Infuse the Oil: Reduce the heat to low. Add the finely minced garlic to the pan with the rendered fat. Sauté for about 30 seconds to 1 minute, until the garlic is fragrant and lightly golden, being careful not to let it burn, as burnt garlic will taste bitter. The kitchen should now smell wonderfully aromatic with the combined scents of garlic and savoury rashers.

Combine Pasta and Sauce: Drain the spaghetti, but do not rinse it. Immediately transfer the hot spaghetti to the frying pan with the garlic-infused oil. Toss vigorously with tongs to coat the pasta evenly, ensuring every strand shimmers with the rich oil.

Create the Emulsion: Remove the pan from the heat. This is crucial to prevent the eggs from scrambling. Pour the egg and cheese mixture over the hot spaghetti, then add about 60ml (a quarter cup) of the reserved pasta water. Toss continuously and vigorously with tongs for 1-2 minutes. The heat from the pasta and the starch in the water will emulsify the eggs and cheese, creating a glossy, creamy sauce that coats the spaghetti beautifully. If the sauce seems too thick, add more pasta water, one tablespoon at a time, until it reaches your desired consistency – it should look rich and flowing, not clumpy.

Final Touches and Plating: Stir in most of the crispy rashers, reserving a small amount for garnish. Taste and adjust seasoning with more black pepper if desired. Serve immediately in warm, shallow bowls. Garnish each serving with the remaining crispy rashers, a sprinkle of fresh Pecorino or Parmesan, and a scattering of finely chopped fresh parsley for a vibrant pop of colour. The aroma of cheese, pepper, and savoury rashers should be inviting and immediate.