Line an 8x8 inch baking pan with parchment paper, leaving a 2-inch overhang on two opposite sides. Lightly grease the parchment with neutral oil or cooking spray.

Heat a dry 10-inch skillet over medium heat. Add pumpkin seeds and toast, stirring constantly, for 3 to 4 minutes until they begin to pop and turn light golden. Remove from heat and set aside.

Combine sugar, honey, and butter in a heavy-bottomed medium saucepan over medium heat. Stir gently until the butter melts and the sugar dissolves, about 3 minutes.

Increase heat to medium-high and stop stirring. Cook the caramel, swirling the pan occasionally, for 6 to 8 minutes until it turns a deep amber color and smells nutty. Watch carefully - it darkens fast near the end.

Remove the pan from heat immediately. Stir in vanilla extract if using, then quickly fold in the toasted pumpkin seeds with a lightly oiled silicone spatula until all seeds are evenly coated.

Pour the mixture into the prepared pan. Working fast, spread it into an even layer with the spatula, pressing firmly to fill the corners.

Sprinkle flaky sea salt evenly over the surface while the caramel is still hot.

Let the slab cool at room temperature for at least 30 minutes until completely firm. Do not refrigerate - this makes the surface tacky.

Lift the slab out of the pan using the parchment overhang. Place on a cutting board and use a sharp chef's knife to cut into 16 bars, pressing firmly straight down rather than sawing.