Make the blueberry sauce: Heat 1 1/2 cups blueberries, 1/4 cup sugar and the salt in a saucepan over medium heat until bubbling. Reduce the heat to medium low and cook, stirring occasionally, until the blueberries are soft, about 5 minutes. Stir in the lemon zest and juice; remove from the heat. Stir in the remaining 1/2 cup blueberries and let the mixture cool to room temperature.
Beat the heavy cream in a bowl with a mixer or whisk until soft peaks just begin to form. Beat in the vanilla and the remaining 1 tablespoon sugar. Gently fold all but 1/3 cup of the blueberry sauce into the whipped cream. Divide among glasses and top with the remaining blueberry sauce. Serve with cookies.