Preheat your oven to 325°F (163°C) and line three half sheet pans 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 evenly distributed.

Melt unsalted butter in a saucepan over medium heat, browning it slightly. Mix in golden syrup and water, then add baking soda.

Pour the warm butter mixture into the flour mixture and gently stir until a greasy dough forms.

Using a cookie scoop, portion the dough into 24 small balls on lined sheet pans, leaving space between each for spreading.

Bake for about 8 minutes until the edges are set but the centers remain soft, then cool on pans for a few minutes.

Prepare the custard filling by simmering water with dry masala chai and fresh ginger for about 10 minutes, then strain.

In another saucepan, combine the strained tea with sugar and whisked egg yolks, then gradually add custard powder and spices until thickened.

Allow the custard to cool to room temperature, then mix in softened unsalted butter until fluffy and smooth.

Pair two cooled cookies and pipe custard filling between them using a pastry bag. Refrigerate custard if too loose.

Serve your cookies alongside a warm cup of masala chai.