Prep: Preheat the oven to 400°F (200°C) and line or grease your baking pan.
Melt the Chocolate and Butter: Add the white chocolate and butter to a heat-safe bowl and melt gently until smooth. Let it cool slightly before continuing.
Add the Wet Ingredients: Mix in the eggs, condensed milk, and vanilla until everything is smooth and well combined.
Add the Flour: Gradually add the flour and pinch of salt. Mix just until there are no dry streaks remaining.
Add the Pumpkin: Fold in the pumpkin purée and mix until the batter has an even color and texture.
Fill the Pan: Spread the pumpkin blondie batter evenly into the prepared baking pan and smooth the top.
Add the Dulce de Leche: Add 3 tablespoons dulce de leche in small spoonfuls over the batter. Gently swirl it into the pumpkin mixture, without completely mixing it in, to create a marbled effect.
Bake: Bake at 400°F (200°C) for about 30 minutes, or until the blondies are set.
Cool: Let the blondies cool completely before cutting so the center has time to firm up.
Decorate: Finish the cooled blondies with stripes of dulce de leche over the top before serving.