Add oil to a skillet. Place over high heat.
When oil is hot and shimmering, add mushroom stems. Sauté for about 15 minutes or until deep golden brown.
After mushrooms are brown, soft and tender, add garlic purée. Sauté for 2 minutes. Do not burn.
Add wine and Marsala. Bring to a boil. Lower heat and simmer until reduced by 1/2.
Add chicken stock. Bring to a boil. Lower heat and simmer until reduced by 1/2.
Add cream and bring to a boil. Reduce to simmer. Skim any impurities that rise to top.
Taste. Add salt and pepper, to taste.
Strain into metal container. Set aside.