Add the dates to a heat-safe bowl and cover with boiling water. Soak for 20 minutes.
Once the 20 minutes are up, preheat your oven to 350°F. Line an 8x8 square baking dish (or 8-inch cake/pie pan) with parchment paper. Drain the water from the dates and add the dates to your food processor. Blend the dates until a sticky paste forms, about 1 minute.
Add the melted chocolate, seed butter, eggs, and vanilla to the food processor. Blend on high speed until very well combined, about 2 minutes. Scrape down the sides of the processor if needed.
Add the oat flour, whole-wheat flour, baking powder, and salt to the food processor. Blend until just combined and no dry flour is left.
Pour the batter into the baking dish, smoothing out the top as much as possible.
Bake in the preheated oven for 25-35 minutes, depending on your pan size and preferred doneness. Let the brownies cool for 15 minutes before serving. (Note: They’re even better after cooling completely.)