Add the butter to the skillet and melt over medium heat, listening for a gentle sizzle. Once melted, let it bubble slightly, filling the air with a rich, toasty aroma.
Pour in the oats and stir quickly with a spatula, coating them evenly with the melted butter. Watch as the oats start to turn golden and emit a toasty smell, toasting lightly in the butter.
Continue stirring gently until the oats are slightly darker and fragrant, about 2-3 minutes. Remove the skillet from heat and stir in the vanilla extract for added aroma and flavor.
Spread the caramelized oats back into an even layer in the skillet, pressing down gently with the spatula to shape them into a compact flat mass.
Let the mixture cook undisturbed for 3-4 minutes until the edges are crispy and golden brown, and you hear a slight crackle at the edges.
Use the spatula to lift up an edge and check for a crunchy, caramel-colored crust. Once achieved, carefully slide the flapjack onto a cutting board or serve straight from the skillet if you prefer a rustic look.
Cut into squares or rectangles while still warm for easy serving. The outside will be crisp with a chewy, caramelized interior.
Serve immediately to enjoy the crunchy edges and warm, chewy center. Enjoy as a satisfying snack or breakfast treat.
