Day Before: Place milk and cream in heavy-bottomed, non-aluminum saucepan. Scald mixture until bubbles form around edges. Add shiitake stems and turn off heat. Cool mixture and let stems steep in cream in refrigerator overnight to intensify mushroom flavor.
Strain mixture the next day and return to heat. While cream is warming, beat sugar and egg yolks with a whisk until mixture is smooth. Pour warm cream over egg mixture, whisking constantly. Return to pan and cook over low heat to avoid curdling. Cook until mixture coats back of a spoon. Strain to remove any lumps. Cool completely.
Churn in ice cream maker according to manufacturer’s instructions.
Recipe and Photo Courtesy of Chef Erin Kem, R Bistro