Reprinted with permission from Ice Pops published in 2015 by Sterling Epicure, an imprint of Sterling Publishing Co., Inc. © Cesar and Nadia Roden.
Put the blackberries, sugar, lime or lemon juice and water in a food processor and blend gradually to a purée.
Pour the mixture into a fine strainer, stir it through and press down on the solids with the back of a spoon to extract all the liquid.
If you want to make stripes, divide the blackberry mixture in half. Add the cream to one half and mix it in well. Pour enough pure blackberry mixture into each ice pop mold to reach about one-quarter of the way up.
Freeze until slightly firm, about 1 hour, then pour the cream mixture on top. Freeze for a further hour, then top with the remaining pure blackberry mixture. Insert an ice pop stick when all the layers are in. They should stay upright due to the half-frozen last layers. Freeze completely.