To make your raspberry sauce, in a medium saucepan add water, raspberries, lemon juice and sugar.
Heat for about 5 minutes over medium high heat until the raspberries break down while you mash them around with a spoon.
Remove from heat and strain out seeds (if desired) through a fine mesh strainer.
Return sauce to pan and place back on heat.
In a small bowl whisk together your 2 Tbs water and cornstarch and stir into sauce for about 1 minute until slightly thickened.
Remove from heat and stir in your vanilla and salt.
Set aside to cool (we place in the freezer).
Meanwhile, in stand mixer or with hand mixer whip your heavy cream until stiff peaks form.
In another bowl mix together your sweetened condensed milk and cocoa powder.
Fold your whipped cream into your cocoa mixture until combined.
Spread half of your chocolate mixture into a bottom of a 9"x5" pan.
Dollop half of your cooled raspberry sauce over the chocolate layer and swirl around with knife or skewer.
Top with remaining chocolate mixture and spread to cover.
Lastly dollop with remaining raspberry sauce and swirl around again.
Cover with Saran Wrap, pressing down so the plastic touches the ice creams surface, this will help prevent ice crystals from forming.
Place another layer of Saran Wrap over the top and place in freezer for 6-8 hour or over night.