Preheat the oven to 350 degrees Fahrenheit.
Add 1/2 cup chopped dark chocolate or chocolate chips to a pot on the stove set to low heat.
Cook, stirring constantly until the chocolate has melted, then immediately remove the pot from the heat (alternatively you can melt the chocolate in the microwave for 20-second intervals, stirring between each, until melted).
Add the melted chocolate, 1/2 cup creamy almond butter, 1/2 cup maple syrup, 1/4 cup cocoa powder, 1/4 cup cold water, 1 teaspoon vanilla extract, and 1/4 teaspoon salt to a large mixing bowl, then use a whisk to mix well.
Add 1/2 cup buckwheat flour and 2 tablespoons ground flaxseed, then use a spoon to stir to combine.
Transfer the brownie batter to an 8-inch square baking dish lined with parchment paper.
Wet your hands with cold water, then use your fingers to press the brownie batter into an even layer.
Bake for 25 minutes.
Let the brownies cool to room temperature before slicing and serving.