The brown route — More like a hunter's ragù. Butter and olive oil, shallot and garlic (paste, if your mortar and pestle is handy), the porcini mix, a tablespoon of tomato paste caramelized to rust-red, then white wine and the soaking liquid, with one of your frozen 2-ounce demiglace cubes melted in. Add a splash of cream at the end if you want it silky, Dijon if you want brightness — that's your classic finishing move anyway. Meatballs browned separately in cast iron first, with their fond stirred into the sauce.

Either way, the meatballs benefit from a little mushroom treatment themselves — wring some rehydrated porcini dry, mince them, and fold them into the pork/beef mix with breadcrumbs soaked in milk. They'll keep the meatballs tender and echo the sauce.

On straining: pour the soaking liquid through a coffee filter or paper towel — dried porcini are notorious for grit, and nothing ruins a delicate ragù faster than sand at the bottom of the bowl.

Meatballs first (pork/beef as usual):

  Minced rehydrated porcini folded into the mix, along with milk-soaked breadcrumbs, egg, grated Parmigiano, garlic paste from the mortar, and a light hand on salt
  Brown them in cast iron in batches — you want a serious fond on the pan, that's your sauce foundation
  Pull them out and reserve; they'll finish cooking in the sauce

The ragù:

  Same pan, butter and olive oil, minced shallot until translucent, then your garlic paste — don't let it brown
  Add the chopped porcini blend (rehydrated porcini + fresh cremini), sauté until they start to catch and their moisture cooks off — this step is where the mushroom flavor concentrates from pleasant to profound
  Tomato paste, about a tablespoon, cooked down until it turns rust-colored and smells sweet
  Deglaze with red wine, scraping everything up, reduce by half
  Now the liquids: strained soaking liquid, one of your 2-ounce demiglace cubes, and just enough stock (your pressure-canned chicken stock would be perfect here) to barely cover — you want this thicker than soup, more like a jus that's going to cling
  Return the meatballs, cover partially, braise at a bare simmer 25–30 minutes