01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together all-purpose flour, cocoa powder, baking powder, baking soda, and salt until evenly mixed.
03 - In a large bowl, whisk melted coconut oil and light brown sugar until smooth and combined.
04 - Add oat milk, dissolved espresso mixture, and vanilla extract to the wet ingredients. Whisk until fully combined.
05 - Gradually fold the dry ingredients into the wet mixture until a soft, cohesive dough is formed.
06 - Scoop tablespoon-sized mounds of dough onto prepared baking sheets, spacing at least 2 inches apart.
07 - Bake in the preheated oven for 10 to 12 minutes, until the cookies are set yet still soft.
08 - Allow cookies to cool on baking sheets for 5 minutes before transferring to a wire rack to cool completely.
09 - Whisk together powdered sugar, cooled espresso, plant-based milk, and a pinch of salt until smooth and pourable.
10 - Once cookies have fully cooled, drizzle or spread frosting over each cookie. Let the frosting set before serving.