1Soak the raisins in the cognac in a small dish for 10 minutes. Combine the tea biscuits, almonds, and cocoa powder in a large mixing bowl. Pour the cognac and raisins into the mixture along with the butter and condensed milk. Mix well with your hands until a stiff, dark, and moist dough is formed.
2Roll a double layer of plastic wrap onto a clean work surface and place one third of the dough into the center of it. Shape the dough into a log about 2 to 3 inches in diameter. Place log towards the end of the plastic wrap and start rolling the plastic tightly around the log. Twist the ends of the plastic like a candy wrapper and tuck them under the log. Repeat with remaining dough. Refrigerate overnight.
3When ready to serve, use a small sieve to sprinkle the outside of the logs with confectioner's sugar, or, if you prefer, sprinkle the confectioner's sugar on a kitchen towel and roll the log on it. Slice with a sharp knife to serve.
1/2 cup raisins
1/4 cup cognac
2 (7 ounce) packages plain tea biscuits, broken into small pieces