Preheat oven to 325°F. Line a 12-cup muffin tin with paper liners, lightly spray the liners with nonstick spray, and set the tin aside.

Make the crust: place 14 Oreo cookies in a small food processor or blender and pulse until fine crumbs form. Stir in 2 tablespoons melted unsalted butter until evenly combined.

Divide the Oreo mixture evenly among the 12 prepared liners (about 1 tablespoon per cup). Press the crumbs firmly into an even layer in each cup. Bake the crusts in the preheated oven for 5 minutes. Remove the pan from the oven and set it aside to cool while you make the filling.

Chop the Butterfinger bars: chop 2 full-size Butterfinger candy bars into small bits for the filling and chop the remaining 1 full-size Butterfinger candy bar for garnish; set the chopped pieces aside.

Make the filling: in a stand mixer (or a large bowl with a hand mixer), beat 12 ounces very soft cream cheese, 1/2 cup full-fat sour cream (room temperature), and 1/3 cup creamy peanut butter until smooth. Add 3/4 cup granulated sugar and beat until smooth, scraping down the sides and bottom of the bowl as needed. Add 2 large eggs plus 1 egg yolk (all at room temperature) and beat until just combined.

Turn the mixer off and, using a rubber spatula, gently stir in 1 1/2 tablespoons all-purpose flour until just combined. Fold in the chopped bits from the 2 Butterfinger bars.

Divide the filling evenly among the 12 crust-lined cups, pouring it on top of the prepared crust layer (about 1/4 cup batter per cup). The cups should be very full but not overflowing. Gently wiggle the pan to level the filling.

Bake in the preheated oven for 22–24 minutes, or until the cheesecakes are puffed, set at the edges, and just a little jiggly in the center. Remove the pan from the oven and place it on a cooling rack. Let the mini cheesecakes cool completely in the pan, then transfer them to the refrigerator to chill for at least 2 hours (until fully set).

Make the peanut butter glaze: place 1/2 cup creamy peanut butter in a small saucepan over medium–low heat and cook, stirring occasionally, until completely melted. Whisk in 1 tablespoon confectioners' sugar until smooth. Let the glaze cool slightly until spoonable.

To finish, top each chilled mini cheesecake with about 1 teaspoon of the peanut butter glaze and garnish with the chopped Butterfinger pieces reserved for garnish.

Store finished cheesecakes in the refrigerator in an airtight container. Cheesecakes kept without the glaze will keep for up to 5 days.