In a small pan, pour the sweetened condensed milk, milk, cornstarch, heavy cream, and the paçocas. Dissolve the cornstarch in the milk before putting in the pan. Cook over medium heat and mix well until it becomes creamy. Set aside.
Repeat the process with the chocolate pudding. Set aside.
In a square tray, put a layer of graham crackers soaked in milk, then a layer of the paçoca pudding, then cover with the graham crackers soaked in milk. Add a layer of the semisweet chocolate pudding. Repeat until the tray is full.
Melt the semisweet chocolate with the heavy cream on the microwave for 1 minute or until it melts completely.
Spread the ganache over the trifle and refrigerate for 4 hours.