In a wide saute pan with high sides, (you may need to use a stock pot) melt 1 tablespoon of the butter and saute the trumpets until wilted, about 3 minutes. Season the trumpets with salt and pepper and then add the wine. Reduce the wine until the pan is nearly dry, then add the milk and stock.
Bring the mixture to a boil, then turn the heat down to a simmer and reduce the mixture until only 25% remains, about an hour or so. Make darn sure that you whisk the reduction as it cooks, the curdles formed by heating the milk will tend to sink to the bottom and stick to the sides of the pan. If they burn there's no going back. After a while the solids will rise to the top and you can let it bubble away without much attention.
When the milk is reduce to 25%, puree the mixture in a blender. The curdles that have formed will emulsify and create a delicious, sweet, creamy sauce. Clean the pan quickly and then add the remaining tablespoon of butter, melt and add the remaining black trumpets.
When the mushrooms are wilted, add the reduced cream to the pan and stir to incorporate. Season the sauce with salt and pepper to taste, then reserve until needed. The sauce will keep in the refrigerator for a week, no prob.