Preheat the oven to 180ºC (350ºF). Line a square 9 x 9 inch (22cm x 22cm) baking pan with parchment paper, allowing the sides to be a bit higher than the top of the pan so it’s easy to pick up and remove the blondies from the pan after it bakes. Set aside.
Melt butter first then set aside to cool for 10 minutes until it’s only slightly warm. Don’t let it firm back up again.
Pour the melted butter into a large mixing bowl. Add both sugars and using a handheld whisk, whisk for 20 seconds until well combined, it will slowly start to thicken and the longer you leave it, the thicker it will get, so be sure not to leave it sitting for too long as it will be harder to whisk through your eggs in the next step.
Add eggs and vanilla, and whisk until well combined, about 15 seconds.
Add the flour, baking powder and salt. Mix with a spatula or wooden spoon until well combined and a firm batter forms.
Add chocolate chips and raspberries. Fold/stir until both are mixed throughout the batter, ensuring not to over-mix.
Spoon batter into the lined baking pan and spread it out evenly. This batter is thick but it does spread out into the pan using a spatula or wooden spoon.
Bake for 25-28 minutes until a toothpick inserted into the middle comes out with only a few moist crumbs on it. If you overbake these blondies, they will lose their soft and fudgy texture.
Remove from the oven and allow it to cool in the pan for 10 minutes.
Gently lift the sides of the parchment paper and transfer to a wire rack to cool completely or slice while it’s still warm if you like a warm and gooey blondie.
Once cool, slice into squares and enjoy!