01 - Combine softened cream cheese, granulated sugar, vanilla extract, and sour cream in a medium mixing bowl. Beat with hand mixer or whisk until completely smooth and creamy, approximately 2 minutes. Set aside.
02 - Arrange tortillas on a clean work surface. Spoon approximately 2 tablespoons of cheesecake filling onto the lower third of each tortilla. If using berries, scatter 1 tablespoon over the filling. Fold the left and right edges inward toward the center, then roll tightly from the bottom upward to form a sealed burrito shape. Secure with toothpicks if necessary to prevent unraveling during frying.
03 - Pour vegetable oil into a deep skillet or saucepan to a depth of 2 inches. Heat over medium-high heat until oil reaches 350°F. Use a kitchen thermometer for accuracy, or test by inserting a wooden spoon handle—bubbles should form steadily around the wood.
04 - Carefully place 2-3 chimichangas in the hot oil, seam side down initially. Fry for 2-3 minutes per side until golden brown and crispy throughout. Remove with a slotted spoon and transfer to paper towels to drain excess oil. Repeat with remaining chimichangas.
05 - Working quickly while chimichangas are still warm, brush each generously with melted unsalted butter using a pastry brush. This helps the cinnamon sugar adhere and adds richness.
06 - Combine granulated sugar and ground cinnamon in a shallow dish, mixing thoroughly. Roll each buttered chimichanga in the mixture, pressing gently to ensure even coating on all sides.
07 - Arrange chimichangas on a serving platter. Serve immediately while warm and crispy. Accompany with whipped cream, additional fresh berries, or warm chocolate sauce if desired.