Preheat and prep: Heat the oven to 350°F (175°C).
Line two baking sheets with parchment paper.
Whisk the dry ingredients: In a large bowl, whisk 1 cup almond flour, 3/4 cup oat flour, 1/3 cup unsweetened cocoa powder, 1/2 teaspoon baking soda, 1/4 teaspoon fine sea salt, and 1/2 teaspoon espresso powder.
Mix the wet ingredients: In a separate bowl, whisk 1/3 cup avocado oil, 1/3 cup maple syrup, 1/4 cup coconut sugar, 1 large egg, and 1 teaspoon vanilla until smooth and glossy.
Combine: Pour the wet mixture into the dry mixture. Stir with a spatula until just combined. The dough will be thick and slightly sticky.
Add the chocolate: Fold in 1/2 to 2/3 cup dark chocolate chips.
If using chopped chocolate, leave some larger chunks for puddles.
Portion: Scoop heaping tablespoons (about 2 tablespoons each) onto the prepared sheets, spacing about 2 inches apart. Lightly flatten the mounds with your fingers or the back of a spoon.
Bake: Bake for 9–12 minutes, rotating sheets halfway. The edges should look set and the centers slightly soft.
Finish: Immediately sprinkle with flaky sea salt if using.
Let the cookies cool on the sheet for 10 minutes to firm up, then move to a rack.
Serve: Enjoy warm for gooey centers, or fully cooled for chewy edges and a denser bite.