Preheat your oven to 350°F (175°C). In a mixing bowl, cream together the softened butter and 1/4 cup granulated sugar until fluffy and light, about 2-3 minutes. Beat in the egg and 1 teaspoon vanilla until well combined. In a separate bowl, whisk together 1 1/2 cups flour, 1/2 teaspoon baking powder, and 1/4 teaspoon salt. Gradually combine the wet and dry ingredients. Press the dough into a 9-inch springform pan and bake for 10-12 minutes until lightly golden. Cool slightly.

In a large mixing bowl, beat 2 packages of softened cream cheese until smooth and creamy, about 2-3 minutes. Gradually add in the 1 cup granulated sugar and 1 teaspoon vanilla extract, mixing until thoroughly combined. Incorporate 2 large eggs one at a time, ensuring each is fully mixed before adding the next. If using, stir in 1/4 cup sour cream and 1 tablespoon flour until the mixture is perfectly creamy and free of lumps.

Once the sugar cookie crust has cooled slightly, pour the cheesecake filling over the crust, smoothing the top with a spatula. Use gentle taps to release any air bubbles trapped in the filling. Ensure the filling is evenly spread out.

Lower your oven temperature to 325°F (163°C) and place the springform pan in the oven. Bake for 40-50 minutes, or until the center is slightly jiggly but not liquid-like. Cover the edges with foil if they brown too quickly.

Once baked, take the cheesecake out of the oven and let it cool at room temperature for about 30 minutes. Then chill it in the refrigerator for at least 3-4 hours, or preferably overnight.

When ready to serve, carefully remove the cheesecake from the springform pan. Garnish with whipped cream, colorful sugar sprinkles, and fresh berries if desired.