These have been a staple of life for my family, friends, picnics, and camping trips for several years. It took a few tweaks to get the formula just right; since then I can practically make them in my sleep. And probably have.
If you want to use white chocolate chips rather than semisweet, go right ahead. A mixture of both? Well, why not. Add nuts? Sure. Especially if they're macadamias. Just be sure to toast your nuts (350 degrees until fragrant) first for that great extra layer of flavor.
Another wonderful variation is to reduce the vanilla extract to 2 teaspoons and add a teaspoon (or more - give the batter a taste) of mint extract, though I'd probably omit any nuts here. Espresso powder dissolved in your vanilla extract - heavenly. A couple of ounces of Kalhúa - oh yeah. The sky may not be the limit, but it's close. And for fall, scoop out a cup of the finished batter; mix in a half cup of canned pumpkin; scrape the un-pumpkinned batter into the prepared baking pan, then splop in the pumpkin batter; use the end of the spatula handle to marble it in. You'll probably need to extent the baking time by 5-7 minutes.
A note on baking and cutting. These beauties are dense - no leavening - so they require some patience before cutting. I find they cut best if made the day before I plan to serve them. Once they're cool, simply wrap the pan well with plastic, store at room temp, then depan and cut the next day after they've had a chance to set up.
And a note on the baking pan. If you use a smaller one, your brownies will take longer to bake by 5 or 10 minutes because they are more dense. If you use a larger one, say a 10" round cake pan as you are welcome to do, they will bake more quickly because of being thinner and less dense, say 5 to 7 minutes less. If you use a 9"x12" pan, you're on your own because they will too thin. They will bake too fast and your family/guests will wonder why they are holding a cookie rather than a brownie.
These freeze very well. During the summer especially, it's nice to have a so to speak rabbit to pull out of a hat without having to scramble for ingredients or turn on a hot oven.
Finally, a note on the healthy option. Cut smaller portions. Go for a hike.
No rabbits were harmed in the making of these brownies.
—boulangere
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