Preheat oven to 350F degrees. Spray 9x13-inch baking dish with nonstick cooking spray (I like the kind that has flour in it).
In a medium bowl, combine cake mix, eggs and melted butter until combined. Batter will be very thick.
Stir in white chocolate chips and walnuts (if using).
Spread mixture evenly into pan.
Bake for about 20-25 minutes, until golden brown and inserted toothpick comes out clean. Baking time will vary so be sure not to over bake.
Allow to cool before cutting into squares.
For the sauce:
In a small bowl, using a whisk, combine sweetened condensed milk with melted butter and maple syrup. Stir well.
If you want to serve this sauce warm, just pop bowl into microwave and nuke it for a few seconds until warm.
Notes
Please note: cake mixes seem to keep reducing in size over the years. Baking times will vary depending on the type of cake mix you purchase and how much is in the box. Not all cake mixes are reducing in size but many are so baking times will now vary depending on the brand. Please understand this before baking. You will need to keep an eye on it. Start with about 15-18 minutes and go from there.
Serve blondie squares with ice cream and drizzle with warm maple butter sauce.
You can use any type of chocolate pieces you like with this.