I preheat the oven to 350°F (175°C) and line an 8x8-inch pan with parchment paper. In a mixing bowl, I cream ½ cup softened butter and ½ cup granulated sugar for 2–3 minutes until light and fluffy. I add ¼ cup brown sugar, 1 large egg, and 1 tsp vanilla extract, mixing until smooth. Gradually, I sift in 1 cup flour, mixing gently to avoid a tough texture, and press the dough evenly into the pan. I bake for 15–18 minutes until the edges are golden, filling the kitchen with a warm, buttery aroma.

While the base bakes, I heat ½ cup heavy cream in a saucepan over medium heat until just simmering, then remove from heat. In a bowl, I whisk ¼ cup granulated sugar and 1 large egg until pale and thick. Slowly, I pour the warm cream into the egg mixture, whisking constantly to prevent curdling. I return the mixture to the saucepan, cooking over low heat for 3–5 minutes, stirring until it thickens and coats a spoon, creating a luscious custard for these creamy cookie bars.

Once the cookie base is baked and slightly cooled, I pour the custard filling over it, spreading evenly with a spatula. I bake for another 15–20 minutes until the custard is set but slightly jiggly. I let the pan cool at room temperature for 30 minutes, then chill in the fridge for 2 hours to firm up the vanilla custard bars.

After chilling, I sprinkle ¼ cup granulated sugar evenly over the custard. Using a kitchen torch, I caramelize the sugar until golden and bubbly, creating a crisp top. If no torch is available, I use the broiler for 1–2 minutes, watching closely to avoid burning, for a perfect crunchy finish on these custard cookie treats.

I slice into 16 squares using a sharp knife dipped in hot water for clean cuts. I serve with a dusting of powdered sugar or fresh berries, enjoying the rich, creamy texture of these vanilla custard bars.