If using gelatin sheets, soften them in a small bowl of cold water for 1 minute; squeeze out excess water. If using powdered gelatin, combine with 1 cup warm water and stir until dissolved.
In a small pot, combine the cream, milk, coffee grounds, sugar, and salt. Bring to a simmer and cook, stirring frequently so the milk doesn’t scorch at the bottom. Gently stir in the sheet gelatin (make sure there is no water in it) or the powdered gelatin dissolved in the warm water. Once incorporated, remove from the heat, cover, and let the mixture steep for 15 to 20 minutes. Strain.
Divide the panna cotta mixture evenly among 4 small serving bowls and refrigerate for 1 hour until set.
To serve, top each panna cotta with biscotti crumbs (optional) and a dash of apple scrap vinegar.
Excerpted with permission from <a target="_blank" href="https://www.amazon.com/gp/product/1455536156/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=1455536156&linkCode=as2&tag=craftfocom-20&linkId=143441747c58fd2c71116809b2fb67ee">Scraps, Wilt & Weeds: Turning Wasted Food into Plenty</a>.