You're going to want to keep the crafting manager's list 'safe' since the code is run both on integrated and client threads, that is to say say to prevent dual thread access errors you'll need
List<IRecipe> l = new ArrayList<IRecipe>();
l.addAll(CraftingManager.instance.getRecipeList());
then iterate the list l to find recipes which have outcomes matching Item.brewingStand
Then use
CraftingManager.instance.getRecipeList().remove(recipe/*the recipe you grabbed through itsra */);