In a large cast iron skillet, add the butter and melt on medium heat. Add the sausage and start cooking it, crumbling it as it cooks. Add the mushrooms and cook for an additional minute until soft.
Add the chicken broth and turn the heat to high. Let the chicken broth simmer down until there's about half the amount there was. Add the cream, salt, pepper, and marjoram. Mix until combined.
Add the xanthan gum 1/4 tsp at a time and make sure to continue to whisk so that the gravy starts to thicken. Once thickened, turn the heat off.
Prepare the biscuits recipe now. I would avoid making the biscuits batter before making the sausage gravy because the baking powder will be in the wet ingredients too long. Once your biscuits batter is ready, add it by the spoonful all over the sausage gravy.
Add the skillet to the oven and cook for 25 minutes.
The biscuits will have absorbed most of the cream from the gravy and will be super flavourful and flaky! It's then ready to serve!
For the biscuits recipe, I used cheddar instead of gouda. You can use any type of shredded cheese you have on hand!