Step 1

In a large bowl, beat the butter and sugars together until light and fluffy with a hand mixer or stand mixer fitted with a paddle attachment.

Step 2

Add the egg, baking soda, milk powder, kosher salt, Thai tea, and vanilla. Beat on medium for 30 seconds.

Step 3

Add the flour and beat on low until almost no dry spots remain. Finally fold in the white chocolate (reserving a few pieces for garnish if you wish). Using a 1/3 cup measuring cup, portion out 100g balls of dough. Freeze for at least 30 minutes while you preheat the oven.

Step 4

Preheat oven to 350F. Evenly space 4 dough balls to a parchment-lined half sheet tray (they spread A LOT and get very large). Bake for 10 minutes. Then pull the tray out and bang it against the counter to release air in the cookies and create ripples. Bake for another 2 minutes and bang again. The cookies should be darker/firmer around the edges and firm yet with a gooey center (if the edges are still soft, bake another 2 minutes). Allow the cookies to cool completely on the sheet. Sprinkle with flaky salt.

Step 5

Repeat with remaining cookies either on a new tray to make the baking process faster or by reusing the original tray if that's all you have. The cookies are best eaten within 2 days.