Preheat the oven to 325°F (160°C).
In a mixing bowl, combine the graham cracker crumbs, melted butter, and sugar. Mix until well combined.
Press the mixture into the bottom of the muffin tin, creating an even layer for each mini cheesecake.
In a separate bowl, beat the softened cream cheese with an electric mixer until smooth and creamy.
Add in the sugar and vanilla extract, continuing to mix until well combined.
Add the eggs one at a time, mixing on low speed after each addition until just combined.
Mix in the sour cream and lemon juice, ensuring the mixture is smooth.
Pour the cheesecake filling over the prepared crusts in the muffin tin, filling each cup about three-quarters full.
Place the muffin tin on a baking sheet and bake in the preheated oven for 20-25 minutes or until the edges are set but the center is slightly jiggly.
Remove from the oven and allow to cool at room temperature. Once cooled, refrigerate for at least 2 hours, or until fully chilled.
Before serving, sprinkle about 1 teaspoon of sugar over the top of each mini cheesecake.
Using a kitchen torch, carefully caramelize the sugar until golden and bubbly. If you don't have a torch, place them under a broiler for 1-2 minutes, watching closely to prevent burning.
Allow the sugar topping to cool for a few minutes until hardened, then serve.