Line a large baking sheet with parchment paper and set aside.
Melt the butter in a medium saucepan over medium-low heat. Add the granulated sugar, corn syrup, and maple syrup. Stir continuously until fully combined.
Increase the heat to medium and bring to a gentle simmer. Stirring continuously, bring the mixture to 250℉, about 7-10 minutes.
Stir in the pepitas, cinnamon, nutmeg, and cloves. Continue stirring until it reaches 275℉, about 10 minutes. Remove the pan from the heat and stir in the vanilla extract and baking soda.
Carefully pour the brittle mixture onto the lined baking sheet and quickly spread the brittle into an even layer. Top with flaky sea salt if desired.
Allow the brittle to cool completely at room temperature for 3 hours, or in the refrigerator for 2 hours. Break apart into pieces and serve.
Notes
To make ahead: Brittle can be made several days or even weeks in advance. It stays fresh at room temperature for 6-8 weeks.
To store: Cool completely and store in an airtight container at room temperature for 6-8 weeks. Do not refrigerate, as the moisture from the fridge will cause the brittle to soften. If storing for longer than 2 weeks, separate the brittle with sheets of parchment or wax paper to prevent any sticking.
To freeze: Cool completely and store in a freezer-safe, airtight container for up to 3 months.
Pepitas. You can use either salted or unsalted pepitas. I prefer unsalted pepitas so I can add flaky sea salt at the end, but salted ones also work. Keep in mind that you may want to omit the flaky sea salt if using salted pepitas.