Heat olive oil in a large skillet over medium-high heat.
Season chicken breasts with salt and pepper, then add them to the skillet.
In the same skillet, add chopped onions and garlic, sautéing until translucent.
Stir in sliced mushrooms and thyme, cooking until mushrooms are golden and tender.
Pour in chicken broth to deglaze the pan, scraping up any bits stuck to the bottom.
Reduce heat and add the heavy cream, stirring well to combine.
Return the chicken to the skillet, allowing it to simmer and absorb flavors for a few minutes.
Adjust seasoning with extra salt and pepper if necessary, then serve warm.