Add the raspberries, sugar and lemon juice to a small saucepan set over medium heat.  Stir to break up the berries and bring to a low boil, stirring occasionally for about 5 minutes.  

Remove the mixture from the heat and pour through a fine-mesh strainer set over a bowl.  With the back of a tablespoon, press the raspberries and juices through the strainer, scraping the underside of the strainer occasionally. Discard the remaining seeds.  

Pour the puree back into the saucepan and set over medium-high heat and bring to a boil. In a small dish stir the cornstarch and water together and whisk briskly into the sauce.  Cook until the puree thickens, about 1 minute.

Transfer the purée to a bowl and set aside to cool to room temperature.

Add the cold water to a small microwavable dish and sprinkle the gelatin evenly over the water and let sit for 5 minutes.  

Set the softened gelatin in the microwave and zap in 10 seconds until syrupy. Stir between intervals. Set aside while preparing the chocolate.

Place the chopped white chocolate into a small dish.

Add the milk to a small saucepan set over medium heat and bring to a simmer, (bubbles forming around the inside edge of the pan.)

Pour 1/2 of the hot milk over the white chocolate, and stir vigorously with a flexible spatula. Stir in the gelatin. (If the gelatin became firm while it sat then give it a quick zap in the microwave to liquefy it again before adding it to the chocolate mixture).

Stir the second 1/2 of the milk into the chocolate and stir until the chocolate is completely melted and the mixture is smooth.

Set aside to cool slightly while whipping the cream.  

Add the whipping cream and the sugar to a large chilled bowl and whip to the stiff peak stage. Gently, fold the cooled white chocolate into the whipped cream, 1/3 at a time until fully incorporated.

Pipe or spoon a layer of mousse into each of 6 small dessert or wine glasses.  Spoon a layer of raspberry puree on top and repeat the layers finishing with mousse on top.  

Set the desserts on a tray, drape a sheet of plastic wrap over them and place in the refrigerator for 12 hours. 

Remove the mousse from the refrigerator 30 minutes before ready to serve. Garnish each serving with fresh raspberries and sprigs of mint.