Butter a 11 by 17-inch rimmed baking sheet, set aside

Melt the butter in a small saucepan over medium heat. Add the brown sugar and agave, stir to combine. Bring to a boil, stirring to dissolve sugar. Continue to cook without stirring, until syrup is medium amber and candy thermometer reads 280 degrees, about 8 minutes.

Stir in pumpkin seeds carefully. Cook until mixture reaches 300 degrees, about 2 minutes. Pour into prepared baking sheet. Let cool. Break into pieces. Store in airtight container.