Line your 8-inch square baking pan with parchment paper, leaving some overhang to easily lift out the bars later.
In a microwave-safe bowl, melt together the peanut butter and butter (or coconut oil) for about 1-2 minutes, stopping halfway to stir until smooth and creamy. You’ll notice it bubbling gently and turning glossy.
Stir in the honey and vanilla extract until fully incorporated. The mixture should be smooth and fragrant, with a slightly sticky texture.
Add the oats and crushed graham crackers to the mixture, folding them in with a spatula until evenly coated. The mixture will become thick and slightly sticky but still easy to stir.
Transfer the mixture into the prepared pan and press it down firmly with the back of a spatula or your fingers to create an even, compact layer. Chill in the refrigerator for about 30 minutes to set.
While it chills, melt the chocolate chips in a small bowl using short bursts in the microwave, stirring between each until smooth and shiny. Add a teaspoon of coconut oil if you want a glossier finish and to help the chocolate spread smoothly.
Pour the melted chocolate over the chilled peanut butter layer, using a spatula to spread it evenly across the surface. Gently shake the pan to help the chocolate settle and smooth out any ripples.
Refrigerate the assembled bars for at least 2 hours, or until the chocolate is firm and the bars are nicely set. This helps the layers meld together and makes slicing easier.
Once set, lift the bars out of the pan using the parchment overhang. Slice into 12 squares with a warm, sharp knife for clean cuts.
Serve immediately or store in an airtight container in the fridge. These bars are best enjoyed within a week for optimal freshness and texture.