Combine vegetable broth or water, thinly sliced shiitake mushroom caps, minced fresh ginger to taste, and dark sesame oil in a small saucepan.

Bring the mixture to a rapid simmer.

Cover the saucepan and simmer gently for 5 to 7 minutes.

In a small container, combine cornstarch with just enough water to dissolve it.

Whisk the cornstarch slurry into the saucepan.

Cook until the gravy thickens.

Remove the saucepan from the heat.

In a small bowl, combine miso with 1/4 cup warm water and whisk until smooth.

Stir the miso mixture into the gravy.

Season with freshly ground pepper to taste.

Serve the gravy immediately, or cover and heat through just before serving.