Toast pumpkin seeds in a dry pan over medium heat, tossing often, until light golden brown. Remove, cool, and set aside.

Butter an 8x8-inch heatproof dish and line with parchment paper. Add pumpkin seeds in an even layer.

Whisk sugar, maple syrup, corn syrup, and water in a heavy-bottomed saucepan and set aside.

Combine pumpkin puree and cream, heating slowly in a small saucepan. Prep butter, spices, salt, and vinegar in separate dishes for quick access.

Heat sugar mixture over medium-high heat until it boils, then reduce to medium heat. Stir occasionally until it reaches 245°F (118°C).

Carefully add warm pumpkin-cream mixture to the caramel, whisking to combine while preventing overflow.

Cook mixture on medium heat until temperature returns to 240°F-245°F (115°C-118°C).

Remove from heat and stir in butter, spices, salt, and vinegar.

Pour caramel mixture into the prepared dish slowly, preserving the pumpkin seed layer. Cool for 10 minutes.

Sprinkle flaky sea salt on top, cooling at room temperature. Chill in the refrigerator for 30 minutes.