In a medium saucepan, combine the heavy cream, milk, cardamom powder, and cinnamon. Give it a stir, and place over medium heat and heat until it starts to steam. Lower down the heat and let this steep, covered, for 30 minutes, making sure it doesn’t come to a boil.

In a heat-proof bowl, whisk the egg yolks and sugar together for 2-3 minutes, until it turns thicker and pale. Next, add in the cornstarch and whisk until combined. Then, pour the spiced milk mixture through a sieve into the bowl, and whisk until everything is combined. Pour everything back into the saucepan, and bring to a boil over medium-high heat while whisking continuously. When the custard comes to a boil, let it cook for another 2-3 minutes, then transfer into a bowl or container. Immediately cover with plastic wrap, making sure the plastic touches the surface of the custard (this prevents a skin from forming). Then, you have two choices here, you can either chill this custard in the fridge until cold, or serve it warm. (I like it chilled.)

Put the butter, dark brown sugar, and salt in a medium saucepan. Place it over medium-high heat and cook until the butter and sugar is completely melted and dissolved into a thick caramel. Then, add in the heavy cream and turn the heat down to a simmer, whisking continuously and cooking it for 5 minutes until thick and syrupy. Then, take it off the heat and let cool to room temperature.

Put 15g (1 tbsp) of butter into a pan, let it melt over medium heat, and put a slice of brioche onto the pan. Weigh down the brioche with a heavy plate or saucepan (this ensures an even crust on the bottom), and let it cook for 1-2 minutes, until the bottom is golden. Flip and repeat for the other side, then transfer onto a wire rack while you repeat this for the other bread slices.

Mix icing sugar and cinnamon powder together in a small bowl.

To serve, while the brioche slices are still on the wire rack, pour 2 tablespoons of butterscotch on top of each slice, and spread it gently with a spoon until the top surface of the brioche is completely covered. Then, put a big ladle of custard into a deep plate or flat-bottomed bowl, place the butterscotch-ed brioche on top, and dust with a teaspoon of cinnamon sugar on top.