Combined cooked condensed milk, 1/2 stick softened butter and 1 tsp lemon juice. Beat them on high speed for 3 minutes.
Spread cream on the wafers, making sure to reach the edges. Just put enough to have the layers stick. You may make 2 skinny cakes or 1 tall one. They do stack nicely when they aren't as tall.
Place cake under a heavy cutting board or make a press using a cutting board with a bowl of water on top. Let it sit under the press at least 2 hours. Then, slice it up and serve.