Heat a medium to large saucepan over medium heat. Add the mushrooms, onions, salt, pepper, and 1 tablespoons of butter. Saute the ingredients for 3 to 5 minutes or until the onions are soft.
8 ounces baby bella mushrooms, ¼ cup white onion, ½ teaspoon salt, ¼ teaspoon ground black pepper
Add the garlic, and continue to cook for 30 seconds. Add the red wine, and deglaze the pan.
1 tablespoon garlic, ¼ cup red wine
Allow the mixture to cook for approximately 2 minutes, just long enough for the alcohol to cook out.
Reduce the heat to low, and add the remaining butter. After the butter melts, stir in the heavy cream. Bring the mixture to a simmer. While stirring, let the mixture cook for about another minute.
½ cup heavy cream
Turn off the heat, and serve.