Add water 1 tablespoon at a time, mixing for 15 seconds between each addition.
3-4 tablespoons water
Continue adding water until dough forms a ball. You might not add all 4 tablespoons of water.
Remove dough from food processor bowl and form a ball. Divide into 6 equal pieces. Place one piece in each mini tart pan.
Using your fingers, press dough evenly down over bottom and sides. Once all areas are covered, use a butter knife across the top of the pan to remove all excess dough. Set each tart pan on a baking sheet.
Filling
Place walnuts on a baking sheet and place in a 350 degree oven for 10 minutes. Stir walnuts lightly halfway through baking time. Remove from oven and let cool.
1 ¼ cups walnuts
Place chocolate in a microwave proof bowl. Microwave for 30 seconds at a time, stirring each time, until chocolate is almost completely melted. Remove bowl from microwave and continue stirring until completely melted. Set aside and let cool slightly.
½ cup semisweet chocolate chips
In a bowl, combine butter, brown sugar, egg and vanilla. Stir in cooled walnuts.
1 tablespoon butter, ¼ cup brown sugar, 1 egg, ½ teaspoon vanilla
Stir in slightly cooled chocolate.
Pour mixture into prepared tart shells.
Bake in a preheated 350 degree oven for 15 minutes. Allow tarts to fully cool on a baking rack before removing from pans.
Video
Notes
You may also use pecans or hazelnuts in place of the walnuts.