Combine all ingredients in a shaker without ice and shake. Add ice and shake once more. Strain into a chilled coupe.
Mushroom SyrupCombine all ingredients, except sugar, in a saucepan and heat on a low simmer for about 20-25 minutes. Strain solids, add the demerara sugar, and stir until sugar is dissolved. Store the mushroom syrup in an airtight container in the refrigerator where it will keep for about a week.