Heat a large pan over medium-high heat. Add the butter and melt it. Add the onions and sauté, for 3 minutes, until they turn translucent and golden. Add the garlic and stir to cook the garlic for about 30 seconds, until fragrant.
Add the chicken broth and white wine to the pan, bringing it to a simmer while stirring. Add the thyme, stir to combine, and reduce the heat to medium-low to simmer the alcohol off for about 10 to 15 minutes, until the sauce has also reduced to half to ⅓ the original amount.
Once the white wine sauce is ready, in a small bowl, combine the cornstarch and 1 tablespoon of water and mix until smooth. Add the cornstarch mixture to the pan, mix to combine, and simmer for 2 minutes to thicken the sauce.
The sauce is now ready to be tossed with cooked pasta or over your favorite protein.
Notes
For an alcohol-free version, use cooking wine, which is located near the balsamic vinegar and oils at the grocery store. It has a nearly identical flavor profile, and it's free from alcohol.