1. Puree the strawberries. Strain through a very fine sieve. Divide into 2/3 and 1/3. Set aside.
2. In a small bowl whisk gelatin and milk. Set aside for 10 minutes.
3. Place heavy cream, milk sugar and salt in a medium saucepan. Bring to a simmer, until sugar dissolves. Do not boil. Remove from heat add vanilla extract. Stir in gelatin and immediately whisk until smooth and dissolved.
4. Add 2/3 of the strawberry puree and whisk until incorporated.
5. Pour into the serving dishes. Cover and refrigerate for at least 3 hours.
6. For the topping: place the remaining 1/3 strawberry puree in a saucepan, add 3 tablespoon sugar and lemon juice. Heat until the sugar dissolves. Remove from heat, let cool and pour over the panna cotta. Refrigerate until serving.