Warm milk in a microwave for 30 seconds.

Add Thai tea leaves to the warm milk and let it steep.

Grease and line a springform or baking pan with parchment paper.

Preheat oven to 350°F (175°C).

Whisk together flour, salt, and baking powder in a bowl.

In a separate bowl, beat softened butter until fluffy.

Gradually add sugar to the butter, beating until well combined.

Add eggs one at a time, beating after each addition.

Strain the tea-infused milk.

Alternately fold in flour mixture and tea-infused milk into the butter mixture.

Pour batter into the prepared pan.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan.

For the custard, combine remaining milk and condensed milk in a saucepan.

Heat over medium-low heat, whisking to combine.

Whisk egg yolks in a separate bowl until smooth.

Slowly pour the hot milk mixture into the yolks, whisking constantly.

Pour the egg mixture back into the saucepan.

Cook over low heat, whisking constantly, until the custard thickens.

Strain the custard through a fine-mesh strainer into a serving container.

Keep covered and warm.

Serve the cake with the warm custard sauce.

Thin the sauce with warm milk if it becomes too thick.