Preheat oven to 350°F. Line an 8 square baking pan with aluminum foil and spray with coconut cooking spray.
Melt chocolate over a double boiler or in the microwave and set aside to cool.
With an electric mixer on medium, beat butter and xylitol until light and creamy, about 4 minutes. Turn speed down to low and beat in eggs, one at a time. Add melted chocolate and blend well. Add almond flour, water, xylitol and extracts (3 tbsp chocolate extract is optional); mix until just combined. Fold in nuts. Transfer batter to prepared pan.
Bake 20 to 25 minutes, until a tester inserted in the center comes out with just a few crumbs. Cool and cut into 16 squares.