Preheat oven to 350°F (175°C)
Make the Crust: Mix crushed graham crackers, sugar, and melted butter. Press firmly into a greased or parchment-lined 9x9-inch pan.
Bake the crust for 8-10 minutes, or until lightly golden.
Make Ganache: In a microwave-safe bowl, heat the heavy cream and chocolate chips in 30 second increments, stirring in between each round in the microwave. Stir until the chocolate has dissolved into the cream and everything is smooth and glossy.
Assemble Layers: Pour the chocolate ganache over the baked graham cracker crust, spreading it evenly. Let it cool for 5-10 minutes at room temperature to slightly set.
Top with Peeps: Arrange the Peeps in a single layer on top of the ganache. Lightly press them in.
Broil for Gooey Peeps: Set your oven to broil and place the pan on the middle rack. Broil for 1-2 minutes, watching carefully, until the Peeps are golden and gooey.
Cool and Eat: Allow your Peeps s'mores bars to cool before digging in. You can eat them warm, or set them in the fridge to firm up a bit. If you let them cool in the fridge, they're easy to cut into smaller bars. I like to let mine set in the fridge for a while until they're actually rather cold.
Store: Store leftovers in the pan you baked them in, covered in the fridge. To serve fresh s'mores bars, slice a bar off and microwave it on a plate for 5-10 seconds to warm it up.