Preheat your oven to 325°F (160°C) and line two baking sheets with parchment paper.

In a large mixing bowl, combine all-purpose flour, quick cooking rolled oats, dark brown sugar, white sugar, and salt. Stir until well combined.

In a saucepan over medium heat, melt unsalted butter until it turns golden brown, about 4-5 minutes. Let it cool before mixing in golden syrup and water.

Pour the cooled butter mixture into the bowl with the dry ingredients. Stir until everything is well combined.

Using a cookie scoop, portion out the dough and place it on the prepared baking sheets with 2 inches apart.

Bake the cookies for approximately 8 minutes, until the edges are golden brown and set.

Let the cookies cool on the sheets for about 5 minutes, then transfer them to a wire rack to cool completely.

Brew your favorite masala chai and let it steep for 5-7 minutes, then strain and let cool.

In a mixing bowl, combine egg yolks with the hot chai sugar mixture and whisk until smooth. Stir in custard powder and masala chai spices.

Add softened butter to the custard mixture and beat until light and fluffy, about 3-5 minutes.

Using a piping bag, pipe custard onto a cookie and top with another cookie to create a sandwich.

Let the cookies set for a few minutes before serving.