If there's one lesson sous chef Miriam Garron of our kitchens learned while developing these bar cookie recipes, it would be 'don't be afraid to make mistakes'!

Although the self-proclaimed dessert-lover delved into hours of research on baking the perfect bar, Miriam ultimately discovered the key to bar cookie success from an oversight in the kitchen. "The baking soda we bought was in a red can that looked just like baking powder…and so we accidentally used that in testing thinking it was powder!"

Baking soda turned out to be a happy accident that Miriam incorporated into the rest of the recipes. "In my head I was envisioning this perfect shiny surface and golden brown color. And that's what it was! Baking soda made the cookies rise outwards rather than up for super-density. I never would have gotten that with baking powder."

Miriam is adamant that consistency is everything in a bar cookie, which lies somewhere in between a regular cookie and a cake with its high density and just the right amount of chewiness. "Cutting a cake in a pan does not equal a bar, and light and fluffy is not a bar." With their capacity for multiple layers and several ingredients, Miriam loves bar cookies as a blank canvas for just about any sweet. "Any dessert can be made into a bar cookie," she says. "Shortbread, tart, banana bread, candy bar. The challenge is a neater, more compact version of the original."

Although Miriam concedes that her favorite is the Apple Crumble Bars (she makes them for bake sales), she loves the versatility and range of the bar cookies she developed. We promise that whether it's a bar cookie for a last-minute bake sale, elegant dessert, or after-school snack, these are the best you'll ever bake — bar none.

• Apple Crumble Bars
• Peanut Butter Jelly Bars
• Banana Bread Bars
• More Bar Cookie Recipes