Combine La Lechera® condensed milk, blackberries, whipped cream and lemon juice. Blend in food processor or blender until smooth.
Take a cup or glass, pour 1-2 teaspoons of the blackberry mixture in the bottom. Cover with Marías biscuits, then add a thick layer of blackberry mixture, repeat. Finish all the glasses and put them in the freezer for 1-1.5 hours, then transfer to the fridge.
Before serving, top with a frozen blackberry and a small piece of dark chocolate if you wish.