*6 tablespoons (3/4 stick) unsalted butter
*3 1/4 cups semisweet choc chips
*1 cup sugar
*1 tablespoon instant coffee granules
*1/2 tsp pure vanilla extract
*1/4 tsp baking powder
*1/4 tsp kosher salt
*1 cup chopped walnuts
*2 to 3 tablespoons heavy cream

Grease and flour a 9-in. tart pan with removable sides.
Preheat oven to 350 degrees
Melt butter in a bowl set over simmering water. Add 2 cups of choclate chips, remove from heat, and stir until the chocolate melts.Set aside to cool completely.
In the bowl of an electric mixer fitted with paddle attachement, beat eggs,sugar,coffee and vanilla on medium-high speed until light and fluffy, about 3 min. Stir in the cooled chocolate. In medium bowl,combine flour,baking powder,salt,1 cup of the chocolate chips, walnuts. Fold the flour mixuture into the batter until just combined, Pour into the pan and bake for 35 to 40 min, until center is puffed.(may crack on top). The inside will still be very soft. Cool to room temperature before removing the sides of tart pan.
Melt the remaining 1/4 cup of chocolate chips with the heavy cream and drizzle on the tart.