In a medium pot, combine the mushrooms, water, veggie scraps, parmesan rind, bay leaf, thyme, and peppercorn together. Bring the ingredients to a boil over medium-heat.
Once boiling, reduce the heat to low. Stir in the truffle seasoning.
Simmer for 1 hour, stirring occasionally.
Remove from heat and season with salt. It's important to wait until the end to salt because if added before, the water will evaporate and your stock could come out overly salty.
Allow to cool completely before straining. The stock can be stored in the fridge for up to a week or frozen for up to 6 months.