In a small bowl, place ½ cup water; sprinkle with gelatin powder, and stir. Let stand 15 minutes to dissolve.
In a medium saucepan, heat milk, cream, ⅔ cup sugar, lemon zest, and tarragon sprig, whisking constantly, just until bubbles form around edges of pan. (Do not boil.) Remove from heat and steep 30 minutes. Strain out tarragon. Add gelatin mixture and return to low heat, whisking until well combined and gelatin mixture has completely dissolved. Pour milk mixture into a pitcher to make it easier to divide later, and let cool completely at room temperature.
Whisk room-temperature milk mixture and skim off any air bubbles. Divide among 8 serving vessels (about ½ cup each). Refrigerate until completely set, 3 to 4 hours.
In a small bowl, stir together strawberries and remaining 1 tablespoon sugar. Refrigerate up to 1 hour.
When ready to serve, top panna cotta with macerated strawberries and garnish with tarragon leaves, if desired.
Kitchen Tip: If making this up to 3 days ahead, cover panna cotta with plastic wrap before refrigerating. Wait until 1 hour before serving to make strawberry topping so the fruit retains its best texture and color.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/tarragon-and-strawberry-panna-cotta/