Preheat oven to 350 degrees F (175 degrees C). Grease a 9-inch springform pan.

Combine digestive biscuits, 1/4 cup chopped walnuts, and melted butter in a bowl; mix well. Press biscuit mixture into the bottom of the prepared springform pan using the back of a spoon.

Bake in the preheated oven until crust is set, about 5 minutes. Set aside to cool.

Beat double cream in a bowl using an electric mixer until soft peaks form. Combine cream cheese and sugar together in a separate bowl until well mixed; add 11.5-ounce jar dulce de leche and eggs, 1 at a time and mixing well after each addition. Avoid over-mixing the cream cheese mixture. Fold double cream mixture into cream cheese mixture until well combined; spoon over the cooled crust.

Bake in the oven for 1 hour 15 minutes. Do not open the oven door while baking. Cool at room temperature for 30 minutes; refrigerate until chilled, at least 3 hours to overnight.

Decorate cheesecake with 2 tablespoons dulce de leche and 1 tablespoon chopped walnuts.