Place a 9x5-inch loaf pan in the freezer to chill.

To a medium saucepan over medium heat, add 2 cups of the blueberries, sugar, and lemon juice. Bring it to a boil. After it comes to a boil, use the back of a spoon or potato masher to gently mash the blueberries. The blueberries should start to break down in 10-15 minutes, resulting in 1 cup sauce.

Remove from heat and set aside to cool completely.

To the bowl of a stand mixer, add the heavy cream. Start mixing at the lowest speed, and then gradually increase speed to medium until the cream starts to get thicker. (The gradual progression prevents you from spraying yourself with cream.)

The cream will thicken and start to peak. Mix on high speed until the cream is thick and stiff. This happens quickly, so watch it closely!

In a medium bowl, combine sweetened condensed milk, vanilla, salt, and 1 cup of whipped cream.

Gently fold the sweetened condensed milk mixture and cooled blueberry sauce into the mixing bowl with the rest of the whipped cream.

Gently fold in the reserved cup of blueberries.

Pour the mixture into the chilled pan and freeze for at least 5 hours, or until fully set up, before serving.