This blackberry cream pie has a layer of blackberry jam topped with a blackberry mascarpone whipped cream in a pistachio brown butter crust.
In the bowl of a stand mixer fitted with the whisk attachment, beat together the mascarpone, whipping cream, and vanilla at medium speed until thickened and able to hold a peak, about 1 to 2 minutes. Reduce the speed to low, add the sugar and honey and mix until *just* incorporated (be careful NOT to overmix). Add the 3 tablespoons reserved blackberry filling and gently fold it into the mixture with a rubber spatula.
Meanwhile, in a food processor or blender, pulverize the graham crackers and pistachios until they form fine crumbs but NOT a paste. They should be dry and crumbly. Combine the brown butter mixture and the graham cracker mixture together in bowl with the sugar and the salt and stir until mixed. Then press into a 10-inch pie dish to form the crust.
Empty the blackberry filling into the crust and spread to even it out. Then add the blackberry whipped cream mixture on top of the blackberry filling and spread it out with a rubber spatula to cover the filling (you can use the back of a spoon to make some fun swirls on top, if you want.) Garnish with the chopped pistachios, honey, and blackberries and place it in the refrigerator for at least 3 hours before slicing and serving. Will keep up to 1 week in the refrigerator in an airtight container, but be aware that the crust will soften the longer it sits.