Whisk all ingredients together in a medium pot. Take care to rub the sage between your fingers to break it down into smaller bits, especially if your brand is a little rustic with bigger leaves and stick pieces (If so, pull out those sticks if you can).
Squeeze the juice out of your lemon wedge completely and discard the rind.
Bring gravy to near boil over high heat, but just before it boils, immediately turn off the heat and remove the pot to a non-hot burner.
Stirring continually, taste and season with black or white pepper and salt as desired.
Notes
Brown rice flour may be substituted for a gluten-free option.