Finally, I scatter the reserved M&Ms and an extra pinch of sprinkles over the top and press them in lightly. This gives the baked bars a professional, bakery-style look. Into a preheated 350°F oven it goes! The magic number for me is 23-25 minutes. The key is to pull them out when the edges are a deep golden brown and the center just looks set—it might even seem a tiny bit underdone. I made the mistake of baking them until a toothpick came out completely clean once, and the bars were dry. They continue to cook as they cool in the pan. Let them cool completely on a rack before lifting out the parchment slab to slice.
Pro Tips for Best Results
I tested the flour question three different ways: all-purpose, a blend, and all bread flour. Bread flour won, hands down. It creates that signature dense, chewy, cookie-shop texture that makes these bars so irresistible. All-purpose flour makes a bar that’s good, but more cakey. If you only have all-purpose, you can use it, but know the texture will be slightly different.
Here’s what I learned the hard way about the butter temperature: patience is key. The first time, I was in a hurry and mixed hot melted butter with my eggs and sugar. It slightly cooked the eggs, resulting in a greasy, grainy dough that baked up oddly. Now, I melt the butter and let it sit on the counter while I gather my other ingredients—just 5-10 minutes to take the fierce heat off makes for a perfectly smooth, emulsified batter.
For the absolute perfect texture and clean slices, you must let them cool completely. I know it’s torture with that amazing smell filling your house, but cutting into warm bars leads to a gooey, crumbly mess. I wait until the pan is cool to the touch, then I use the parchment paper to lift the entire block onto a cutting board. Using a sharp chef’s knife (not a serrated one), I slice straight down for clean edges. This waiting period is the final, crucial step to bakery-quality bars.
Common Mistakes to Avoid
My first batch was a lesson in overbaking. I kept poking them with a toothpick, waiting for it to come out clean like a cake. By the time it did, the bars were overdone—dry around the edges and lacking that wonderful soft center. Don’t do what I did! These bars are ready when the edges are browned and the center looks just set, even if it jiggles slightly. They firm up perfectly as they cool. It’s better to err on the side of underdone.(See the next page below to continue…)