Preheat the oven to 375°F (190°C). Line two large baking sheets with parchment paper.
In a large bowl, whisk together ¾ cup cane sugar, ¼ cup packed light brown sugar, and 1 tablespoon matcha powder until evenly combined.
Add 1 cup melted coconut oil to the sugar–matcha mixture and whisk until smooth and well combined.
Add 1 large egg and 1 large egg yolk to the bowl and whisk until incorporated. Stir in 1 teaspoon vanilla extract.
Sprinkle ½ teaspoon baking soda and ½ teaspoon sea salt over the mixture and whisk briefly to distribute.
Add 2½ cups all-purpose flour (spooned and leveled) to the bowl. Use a rubber spatula to fold and mix until the dough is just combined; do not overmix.
Using a 2-tablespoon cookie scoop (or spoons), portion the dough into 2-tablespoon mounds onto the prepared baking sheets, leaving about 2 inches between cookies.
Bake one sheet at a time in the preheated oven for 8 minutes, or until the cookies are puffed and the edges are lightly set. (If your oven fits both sheets without crowding, you may bake both at once but rotate the sheets front-to-back halfway if needed for even baking.)
Remove the baking sheet from the oven and let the cookies cool on the sheet for 5 minutes, then transfer the cookies to a wire rack to cool completely before decorating.
To make the white chocolate dip, place about 1 inch of water in a small saucepan and bring to a gentle simmer over medium heat. In a medium heatproof bowl, combine 1 cup white chocolate chips and 1 teaspoon coconut oil. Set the bowl over (not touching) the simmering water and stir occasionally until the chocolate is fully melted and smooth. Remove the bowl from the heat.
Dip one side of each completely cooled cookie into the melted white chocolate, letting excess drip back into the bowl. Place dipped cookies on a sheet of parchment paper and immediately sprinkle with black sesame seeds.
Let the dipped cookies sit at room temperature for about 20 minutes, or until the white chocolate is firm.
Store cookies in an airtight container at room temperature for up to 4 days, or freeze for up to 3 months.
Notes
13. Store cookies in an airtight container at room temperature for up to 4 days, or freeze for up to 3 months.