Preheat the oven to 150 degrees Celsius. Place two ramekins in a deep roasting pan. Boil a kettle of water.
Place the heavy cream in a small pot. Heat the cream over medium to medium-low heat until the cream comes to a simmer (small bubbles appearing on the side of the pot). Don't let it boil and bubble vigorously.
While the cream is heating, place the egg yolks in a heat-proof bowl. Add in the sugar and whisk with a wire whisk until some of the sugar has been incorporated.
When the cream has come to a simmer, scoop a ladleful of hot cream and pour it in a slow and steady stream into the egg yolks, whisking it all the time to bring up the temperature of the eggs. This is called tempering.
Stir in the remaining cream, taking care to stir gently and not whisk anymore to prevent incorporating too much air into the custard. Stir in the Baileys.
Strain the custard into a measuring jug and divide it among the two ramekins. Use a small spoon to scoop out the foam and bubbles on the surface of the custard.
(The straining and scooping of foam and bubbles are optional steps, but they helped to make a smooth and pretty crème brûlée.)
Fill the roasting pan with the boiling water until the water level reaches halfway up the sides of the ramekins.
Bake for 20 to 25 minutes, until the crème brûlée is just slightly wobbly in the centre. The top should remain pale in colour and not browned.
Remove the ramekins from the hot water bath and let it cool to room temperature. Refrigerate for at least 4 hours (preferably overnight) and up to 3 days.
Broiler: Freeze the crème brûlées for 30 minutes and preheat the broiler. Sprinkle sugar evenly on the top and broil for 3 - 5 minutes, until the sugar has caramelized. Blowtorch: Remove the crème brûlée 15 minutes from the refrigerator before serving. Sprinkle sugar evenly on the top and melt and caramelized the sugar using the blowtorch, taking care not to burn the sugar too much.
Leave the crème brûlée aside for 1 minute and serve immediately.