In a medium bowl, whisk together honey, soy sauce, minced garlic, apple cider vinegar, garlic salt, and red pepper flakes (if using). Set aside.
In a large skillet over medium-high heat, combine chicken broth and heavy cream. Stir and bring to a gentle boil.
Add uncooked spaghetti to the skillet, fanning it out or breaking in half if needed to fit mostly flat. Use tongs to stir and separate noodles, coating them in the liquid.
Reduce the heat to medium-low. Cover and simmer 10-12 minutes, stirring occasionally, until pasta is al dente and most liquid is absorbed.
In a small bowl, whisk cornstarch and water to make a slurry.
Pour the reserved honey-garlic sauce into the skillet. Stir well, then add cornstarch slurry immediately. Simmer uncovered 2-3 minutes, stirring often, until sauce thickens and coats pasta.
Remove from heat. Sprinkle with grated Parmesan cheese.
Garnish with chopped fresh parsley and extra red pepper flakes if desired. Serve hot.