Pumpkin Seed Toffee

1. Step 1Line a 13″ x 9″ pan with parchment, leaving an overhang on both 2 long opposite sides. In a large (at least 3-quart) heavy pot over medium-low heat, cook butter, sugar, allspice, cinnamon, kosher salt, ginger, and nutmeg, stirring constantly, until butter is melted and sugar is dissolved, 3 to 5 minutes. Bring to a simmer and cook, stirring frequently, until an instant-read thermometer registers 290° to 300° and mixture turns a deep amber color, about 10 minutes. If mixture breaks or separates, whisk until toffee is emulsified, being careful not to splash your hands with hot toffee.
2. Step 2Remove pot from heat. Stir in pepitas. Pour toffee into prepared pan and smooth in an even layer. Let cool completely, about 1 hour.
3. Step 3Break toffee into small pieces. Dip half of each piece into melted chocolate and return to parchment-lined pan. Sprinkle with sea salt (if using). Let sit until chocolate is hardened, about 30 minutes.