Lay out all your ingredients before you turn on any burner. Slice the chicken breasts thin if they aren't already, and mince the garlic cloves finely. Having everything measured and ready keeps the cooking process quick and stress-free.
Heat olive oil in a large skillet over medium heat until it shimmers slightly. Season the sliced chicken with salt, pepper, bouillon, garlic powder, paprika, and thyme. Cook for 6 to 8 minutes total, flipping once, until both sides turn deep golden brown, then set the chicken aside.
While the chicken cooks, bring a large pot of salted water to a rolling boil. Add the spaghetti and cook according to the package directions until it's just al dente. Drain it in a colander, but don't rinse it, since the starch helps the sauce cling.
In the same skillet you used for the chicken, melt the butter over medium heat, scraping up any browned bits left behind. Add the minced garlic and red pepper flakes, stirring constantly for about a minute until fragrant. Watch closely here, since garlic burns quickly and turns bitter.
Return the cooked chicken to the skillet with the garlic butter sauce. Add the drained spaghetti directly into the pan and toss everything together so the noodles soak up all that buttery flavor. Sprinkle in the freshly grated parmesan and toss again until it melts into the sauce.
Taste the pasta and add a pinch more salt if it needs it. Plate the pasta while it's hot, then top with a little extra parmesan and a sprinkle of fresh parsley. Serve immediately for the best texture and flavor.