Grate some stale bread into breadcrumbs. You want largish pieces.
Bring a large pot of salted water to a boil. Add the spaghetti and cook until al dente.
As soon as you add the pasta to the pot, heat a large skillet over medium heat and add the oil.
Add the garlic slices and cook, stirring, until the garlic is sizzling but don't let it darken.
Add the bread crumbs and stir well to coat them with the oil.
Keep stirring and tossing as they start to toast.
Sprinkle the dried oregano over the bread crumbs and keep stirring.
Lower the heat and cook until the bread crumbs and garlic are golden and crisp but not overdone.
Turn off the heat.
Check the pasta periodically. As soon as it is done al dente, lift it out of the water, let it drain for a bit and then add to the skillet. It's helpful to use tongs and a spider for this step.
Turn the heat back on and toss the pasta with the bread crumbs and garlic. Salt with 1/4 teaspoon salt and toss.
If the bread crumbs absorb all the oil and the pasta seems dry, add more olive oil and toss.
Taste and season with more salt if needed.
Sprinkle the parsley and cheese on the pasta, toss and serve.