Preheat the oven to 180°C (350°F).

In a food processor, crush the digestive biscuits until they become fine crumbs. Pour the melted butter over the crumbs and mix well until the mixture resembles wet sand.

Press the biscuit mixture evenly into the bottom of a 9-inch (23 cm) springform pan to form the crust. Place the pan in the refrigerator while preparing the filling.

In a large mixing bowl, beat the cream cheese, peanut butter, and granulated sugar until smooth and creamy.

Add the eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl as needed.

Mix in the sour cream and vanilla extract until well combined.

Pour the filling over the prepared crust in the springform pan, smoothing the top with a spatula.

Bake in the preheated oven for 60 minutes or until the edges are set and the centre is slightly jiggly.

Turn off the oven and leave the cheesecake inside for an additional 30 minutes with the oven door slightly open.

Remove the cheesecake from the oven and let it cool completely at room temperature.

While the cheesecake is cooling, prepare the peanut butter sauce. In a small saucepan, melt the peanut butter over low heat. Stir in the powdered sugar and milk until smooth and well combined. Remove from heat and let it cool slightly.

Once the cheesecake has cooled, carefully remove it from the springform pan. Drizzle the peanut butter sauce over the top of the cheesecake.

Place the cheesecake in the refrigerator to chill for at least 2 hours or overnight before serving.