Add the vanilla and salt. Mix for 30 seconds, until the filling smells sweet and nutty.

Add the powdered sugar 1 cup at a time, mixing on the lowest speed for 1 minute after each, until the mixture looks like damp sand and clumps when squeezed.

Stir in the graham cracker crumbs with a spatula for 1 minute, until the dough pulls together into a soft mass with no dry streaks.

Scoop level tablespoons and roll each into a smooth, round 1-inch ball (36 in all, about 12 minutes). Set them 1/2 inch apart on the parchment-lined baking sheet. Rinse your hands under cold water after every dozen balls.

Refrigerate the baking sheet for 30 minutes, until the balls feel cold and firm and a fingertip leaves no dent. Line a second baking sheet with parchment.

Microwave the chocolate chips and coconut oil at 50% power for 1 minute, then stir. Continue in 20-second bursts, stirring each time, until a few chips remain (2 to 3 minutes in all). Stir off the heat until the chocolate is glossy and falls from the spoon in a ribbon.

Drop one cold ball into the chocolate, roll it with a dinner fork, and lift it out. Tap the fork 3 times on the bowl rim and hold it level for 2 seconds. Slide the ball onto the second sheet, where the shell should look glossy with no peanut butter showing.

Refrigerate the dipped balls for 15 minutes, until the shell looks matte instead of shiny and the base feels dry.