Preheat oven to 180 degrees Celsius. Toast the black and white sesame seeds on separate trays until the white sesame seeds is lightly golden, about 5 to 7 minutes. Remove from the oven and let cool completely.
In a food processor, grind the white sesame seeds with 1 teaspoon of honey until fine. Repeat with the black sesame seeds. Set the sesame pastes aside.
Weigh your empty mixing bowl and note it down. Place the butter and sugar in the mixing bowl. Using an electric mixer, cream the mixture on high speed until light and fluffy, about 5 minutes. Add in the egg yolk and beat on medium speed until incorporated, about 1 minute. Now weigh your mixing bowl again, subtract the weight of your empty mixing bowl and scoop out half of the dough into another mixing bowl.
Mix in 1/2 of the flour (77 grams) and the black sesame paste into one portion of the dough and the remaining flour and white sesame paste into the other portion. If the dough is too stiff, mix in drops of milk until soft enough to handle.
Wipe the table top with a damp cloth and line a plastic wrap on top (so that the plastic wrap will stay in place). Place the black sesame dough on top of the plastic wrap and shape it into a 4 x 7.5-inch block. Wrap the dough with the plastic wrap and chill in the refrigerator for 30 minutes to 1 hour. Repeat for the white sesame dough.
While the doughs are still cold, slice both doughs into 0.5 x 7.5-inch strips (or equally into 8 strips). Brush each strip of dough lightly with milk and join them together to form a chequered shape, pressing them together gently. Wrap the chequered dough with plastic wrap and chill in the refrigerator for 1 hour. (See pictorial guide below.)
At this point, you can also freeze the dough until you need it. There is no need to thaw the dough, just add 1 to 2 minutes to the baking time.
Preheat the oven to 160 degrees Celsius. Line a baking sheet with parchment paper.
Slice the chequered dough into 1/4-inch thick slices and place them on the baking sheet. Bake for 10 to 12 minutes for large chequered cookies and 8 to 10 minutes for small chequered cookies, until the edges are lightly golden. Let the cookies cool completely on a wire rack before storing it in an airtight container.
NOTES
- Use a small food processor as the amount of sesame seeds is very little. If you don't have a food processor, pound the sesame seeds in a pestle and mortar then mix in the honey. - Adapted from Nami's (Just One Cookbook) Sesame Cookies