Preheat the oven to 350°. Grease and flour an 8-inch square baking pan.
Melt the butter and chocolate together in the microwave or in a bowl over a pan of simmering water. Remove when melted and scrape the mixture into a large bowl. Add the sugars and stir with a wooden spoon to combine. One at a time, add the eggs and continue to mix with the spoon. With the last egg, stir in the vanilla. Fold in the dry ingredients (mix together in advance) until just combined, then fold in the hemp seeds.
Pour the batter into the prepared baking pan and bake for 20–25 minutes, until the brownies are pulling away from the sides of the pan and feel set if you touch them gently on top. Allow to cool in the pan before cutting into squares.