Preheat the oven to 300 degrees F.
Pour the milk into a medium saucepan and add 1 tablespoon of the sugar, the cardamom and bananas, mashing them a bit into the milk. Turn the heat to medium-high and when it comes to a boil, turn the heat off and cover the pan with a tight-fitting lid. Leave to infuse for 15 to 20 minutes.
In a medium bowl, beat the egg yolks with 1 tablespoon of the sugar until thick and pale. Strain the hot milk, and then slowly pour it into the egg yolk mixture, whisking constantly to prevent the eggs from scrambling. Pour the mixture back into the saucepan and cook over low heat until the mixture is thick enough to coat the back of a spoon, 3 to 5 minutes.
Pour the mixture into 4 shallow creme brulee dishes or ramekins, place in a baking pan large enough to accommodate them and pour enough water into the pan to come halfway up the dishes. Bake until set but still slightly jiggly, about 30 minutes. If they aren't done at this point, continue to check them every 5 minutes until they are set. Remove from the water bath and let cool slightly on the counter top. Put them in the refrigerator to finish cooling for about an hour.
Sprinkle 1 tablespoon of the sugar evenly on top of each creme brulee. Melt the sugar with a blowtorch, or alternatively place under a broiler until it has caramelized. Serve immediately.