Start by making your crust. Preheat oven to 350 F and line a muffin tin with cupcake liners.
Add chocolate graham crackers to bowl of food processor and pulse until finely ground. In a small bowl, combine graham crackers, melted butter, and salt. Mix until the crumbs stick together nicely.
Press mixture into a thin layer covering bottom and sides of cupcake liners. Freeze crust for 10 minutes.
Bake for 10 minutes and then transfer to a wire rack and let cool completely before filling.
For the filling, place 1/2 cup of peanuts, peanut butter chips, chocolate chips, sugar, espresso powder, cinnamon and nutmeg in the bowl of your food processor. Pulse until peanuts and chips are in little pieces. Transfer mixture to a bowl and set aside.
In a separate medium-sized bowl, whip 2 cups of heavy cream until it holds medium peaks. Slowly add 1/4 cup of powdered sugar and whip until cream holds medium-firm peaks. Transfer whipped cream to fridge until needed.
In a large bowl, beat cream cheese with remaining 1 cup of powdered sugar until cream cheese is smooth. Add in peanut butter, whole milk, and 1/4 cup of chopped peanuts and mix until well combined.
Gently fold in about 1/4 of whipped cream to lighten the mixture. Stir in chocolate chip & peanut mixture. Then slowly fold in remaining whipped cream.
Fill each cupcake liner about 3/4 full of filling. Refrigerate for about 3 hours, or until filling is set.
For chocolate ganache topping, carefully melt remaining chocolate chips in microwave-safe bowl in 30 second intervals. When chocolate is melted, pour in heavy cream, and mix until combined with chocolate.
Pour chocolate over each mini tart and smoothing with a spoon, if desired. Chop remaining 1/2 cup of peanuts and scatter over top of tarts. Chill for at least 20 minutes, or until chocolate is set.