Cut 15 sheets of phyllo dough into triangles. Brush them with melted butter, then bake on the top and bottom racks until golden brown.

To make the filling, mix the whipped topping powder with cold milk using a mixer until creamy, then add the cream cheese and blend until smooth.

Prepare the syrup by heating sugar, water, and lemon juice on the stove until it boils. Let it cool. Remove the warbat from the oven, pour the cooled syrup over the hot pastries, and let them cool completely.

Split each pastry open in the center, fill with the cream mixture, sprinkle with chopped pistachios, and serve on a platter.