Start by boiling well salted water for pasta in a very large pot (pasta needs a lot of water to cook properly). Add the salt just before it starts to boil to protect your pot.
Next, fry the bacon pieces until cooked, but not crispy.
The pasta should be in the water and starting to cook by this point.
Beat the eggs in a large jug. Add the cream and milk. Stir well, and add about ¼ tsp salt and quite a bit of black pepper.
Add in the grated Pecorino Romano or Parmigiano cheese.
When the pasta is al dente, drain it and reserve some water, and put back in the same pot (if you used a colander) and back on the burner, over the lowest heat possible (just warm.) Alternatively, put the pasta into a large saucepan or wok using a pasta fork to remove it from the pot.
Add in the bacon pieces and stir gently.
Now add the egg mixture from the pyrex jug.
Stir well to combine evenly. The eggs will cook from the heat of the pasta, so quickly turn off the burner as soon as the sauce starts to thicken. If you put the heat on too high, or leave it on too long, you can curdle the sauce, so don't forget to turn off the burner. Add some reserved pasta water if it's too thick.
Serve hot with extra grated cheese and pepper, if desired.