2 teaspoons plus 3/4 cup butter, softened, divided
1/3 cup light corn syrup
2/3 cup sugar
1/2 cup sesame seeds, toasted
Line a 15x10x1-in. pan with foil and grease the foil with cooking spray; set aside.
Grease the sides of a large heavy saucepan with 2 teaspoons butter. Add the corn syrup and remaining butter; cook over medium heat until butter is melted. Add sugar and sesame seeds; cook and stir until mixture comes to a boil. Cook and stir until mixture turns a golden brown and a candy thermometer reads 300° (hard-crack stage).
Pour into prepared pan (do not scrape sides of saucepan). Spread evenly. Cool; break into pieces.