Make sure your ingredients are ready to go before beginning. Wash, pat dry, and slice your mushrooms. Dice the onion. Mince the garlic. If you are using any fresh herbs, make sure they are washed and minced.
Add the butter to a heavy skillet over medium heat. Let it melt but not bubble.
Add the onion, sprinkle with a pinch of salt, and saute for about 5 minutes.
Add the mushrooms, sprinkle with a pinch of salt, and saute for at least 5-7 minutes. We want them to release some of their liquid, so expect them to steam and shrink. Stir as needed.
Add the garlic and all spices. Saute for 1 minute.
Stir in the vegetable stock or bone broth and simmer for 1-2 minutes.
Decrease the heat to medium-low. Add the half and half, gently stirring to combine.
Cook until the mixture thickens, about 7-9 minutes.
Taste and adjust the salt and pepper levels if needed.
Remove from heat. If using now, continue to the next step. If making ahead, let it cool to room temperature, then store in an airtight container in the fridge.