Instructions

• Make the cherry jam: Put the 6 ounces pitted tart cherries and 1/4 cup peeled, finely grated Granny Smith apple into a food processor. Pulse briefly until the fruit is broken into mostly pea-sized chunks (do not puree). If using frozen cherries, do not thaw first.
• Transfer the pulsed cherries and apple to a large saucepan. Add 1/2 cup granulated sugar and set over medium-high heat. Bring to a simmer, stirring occasionally, then continue to cook 10–15 minutes, stirring fairly regularly, until the mixture is very thick and jam-like. Watch carefully to prevent scorching. Remove from heat and let cool to room temperature. (Jam can be made a few days ahead and refrigerated.)
• Make the crust: Put 1 1/2 cups chocolate wafer cookie crumbs (from about 7 ounces cookies) into a food processor and pulse until finely ground. Add 2 tablespoons granulated sugar and 1/8 teaspoon fine sea salt and pulse a few times to combine.
• Melt the crust butter and chocolate: In a microwave-safe bowl, microwave 5 tablespoons unsalted butter (cut into chunks) for about 30 seconds or until mostly melted. Add 2 ounces finely chopped dark or semisweet chocolate to the butter and stir. If the chocolate is not fully melted, microwave the bowl at half power in 15-second intervals, stirring after each interval, until the chocolate is just melted and the mixture is smooth.
• Combine crumbs and chocolate: Pour the melted butter–chocolate mixture into the cookie crumbs and fold until the crumbs are evenly moistened.
• Press the crust into the pan: Dump the crumb mixture into a 9-inch round tart pan with a removable bottom (or a 13.75-by-4.5-inch rectangle pan). Press the crumbs firmly and evenly onto the bottom and up the sides (use a tamper, the bottom of a measuring cup, or a small flat-bottomed glass to help). Refrigerate the crust at least 30 minutes, until firm.
• Prepare the chocolate filling: Place 7 ounces finely chopped good-quality dark chocolate (70–75%) in a heatproof bowl. Heat 3/4 cup of the heavy whipping cream in a small saucepan until it just begins to bubble (do not let it fully boil). Pour the warm cream over the chopped chocolate and let sit 30 seconds. Whisk gently, starting in the center and working outward, until the chocolate is melted and the mixture is smooth.
• Add butter and vanilla to filling: Add the 1/4 cup unsalted butter (cut into chunks) to the chocolate mixture one chunk at a time, whisking slowly to incorporate each chunk before adding the next. Stir in 1 teaspoon vanilla extract.
• Whip and fold the remaining cream: In a clean bowl, vigorously whisk the remaining 1/2 cup heavy whipping cream until it holds soft peaks (soft mounds that fold over slightly). Gently fold the whipped cream into the melted chocolate mixture until the mixture is smooth and no white streaks remain.
• Assemble the tart: Spread the cooled cherry jam in an even layer in the chilled crust. Pour the chocolate filling over the jam and spread into an even layer.
• Chill and serve: Refrigerate the assembled tart until set, at least 2 hours or overnight. Before serving, lift the tart out of the pan using the removable bottom and slice into pieces.