Step 1

Lightly grease (or line with parchment) a 9” square pan.

Step 2

, In a medium saucepan set over medium heat, melt and stir together the butter, brown sugar, and syrup, cooking until the sugar has dissolved.

Step 3

, Stir in the oats, flour, salt, and graham cracker crumbs.

Step 4

, Press slightly more than half the mixture (about 330g) evenly into the prepared pan. Let cool completely.

Step 5

, While the crust is cooling, preheat the oven to 350°F.

Step 6

, Sprinkle the chocolate chips evenly over the crust, then the marshmallows.

Step 7

, Top with the remaining crust mixture.

Step 8

, Bake the bars for 15 to 20 minutes, until the crust is light gold and the marshmallows are puffed and lightly browned.

Step 9

, Remove the bars from the oven and let them rest for 20 minutes, then cut into squares or rectangles while still slightly warm.

Step 10

, Store completely cooled bars, well wrapped, at room temperature for up to four days; freeze for longer storage.