01 -
Line a rimmed baking sheet with parchment paper and lightly butter the parchment. Set the pan near the microwave before you start.
02 -
Stir the sugar and corn syrup together in a large microwave-safe glass bowl. Microwave on high for 4 minutes, until the mixture is bubbling strongly and looks clear.
03 -
Carefully stir in the peanuts. Microwave on high for 3 to 4 minutes, stopping when the syrup turns light amber and smells toasted.
04 -
Stir in the butter and vanilla with care, since the syrup will sputter. Microwave on high for 1 minute, until bubbling again.
05 -
Immediately stir in the baking soda and optional salt. The mixture will foam and lighten. Stir only until evenly combined.
06 -
Quickly pour the foamy brittle onto the prepared pan and spread gently with a buttered spatula. Cool for 30 to 45 minutes, then break into pieces.