Start by adding the bacon and sprouts to a lined baking tray. Drizzle 1 tbsp of olive oil onto the tray and use your hands to coat the ingredients. Season with salt and pepper & pop the tray in the oven for 20 - 25 minutes.
After around 15 minutes, add the spaghetti to salted, boiling water and set your timer according to the packet.
When your pasta is almost ready, whisk 3 egg yolks & 1 egg in a large mixing bowl, season with black pepper and stir in half of the grated parmesan. Pour a splash of pasta water (approx 50ml) into the bowl, whisk vigorously. The residual heat from the pasta water & spaghetti (about to be thrown in) will cook the egg yolk, don’t sweat!
At this stage, the bacon & brussels should be crispy and ready to come out of the oven. Set aside whilst you transfer the cooked pasta into the mixing bowl with the eggs. Rapidly stir the spaghetti in the whisked eggs and add a ladle of pasta water and gradually add the parmesan whilst stirring (preventing clumps of cheese).
You may need to add another ladle of pasta water once you’ve poured all of the parmesan into the bowl as the parmesan absorbs and thickens the sauce a lot. Season with lots of black pepper and fold half of the sprout/ bacon mix into the bowl, reserving half to serve on top