Preheat the oven to 300°F (150°C). Lightly grease the interior of an 8-inch (20cm) springform pan with butter, coating the bottom and sides. Line the base of the pan with a circle of parchment paper and place the pan on a baking sheet.

In a medium, microwave-safe bowl, microwave the butter until melted. Put the graham crackers or the digestive biscuits in a zip-top bag and crush them to a fine texture with a rolling pin. Add the crushed graham crackers to the butter and stir to combine.

Transfer the butter/crumb mixture into the prepared springform pan. Using the back of a tablespoon, distribute and press the crumb mixture to form an even layer on the bottom of the pan.

In a stand mixer fitted with a paddle attachment (or a large bowl, if using a hand mixer), beat the cream cheese, sour cream, and vanilla on medium speed until smooth, about 30 seconds. With the mixer running at low speed, add the sugar in a stream. Increase the speed to medium and continue beating the mixture for about 1 minute until it looks uniform.

Add the eggs one at a time, beating the mixture to incorporate each egg before adding the next. As soon as the eggs are incorporated, stop mixing. Add the flour 1 tablespoon at a time and then the salt, continuing to beat on medium-low speed until incorporated.

Using a rubber spatula, scrape the bottom and sides of the bowl. Give one last mix on low speed for about 20 seconds.

Transfer the cheesecake filling onto the prepared crust. Smooth the surface of the filling using an offset spatula. Gently tap the pan on the countertop a few times to release any air bubbles that might have formed.

Bake for 1 hour. The edge of the cheesecake should be set, but the center should wobble when you give the pan a nudge. Turn the oven off and leave the cheesecake in the oven with the door closed for 20 minutes. Then, open the oven door and allow the cheesecake to sit for another 10 minutes.

Carefully remove the cheesecake from the oven and allow to cool completely in the pan at room temperature. When cool, cover with a plate, and refrigerate for at least 8 hours or ideally overnight.

Gently run a knife around the edge of cheesecake to release it from the sides of the pan. Remove the cheesecake from the pan and place on a serving plate. Cut into slices and serve with fresh strawberries and a little strawberry sauce, if desired.