Combine chopped strawberries and 3 tablespoons sugar in the bowl and let stand for 10 minutes. Blitz in a food processor until smooth. Pour 2 tablespoons water in a large bowl, and sprinkle with gelatin. Place over a pan of boiling water to dissolve the gelatin. Place the cream and vanilla essence in a large bowl and beat with a mixer at high speed until stiff peaks form. Gently fold in half of strawberry mixture, along with the dissolved gelatin. Spoon some of the mixture into your serving glasses followed by a little of the remaining strawberry sauce. Repeat the process of layering the mousse and the sauce until the glasses are full. Place in the fridge to chill and set for an hour before serving decorated with extra strawberries and mint leaves.