Line a large (18x26 inch) sheet pan with lightly buttered parchment paper or a silicone mat to ensure easy removal once the brittle hardens. Set aside.

To a large (3-4 quart) stainless steel sauce pot add the water, granulated sugar, and corn syrup. Gently stir to combine. Place a candy thermometer onto the side of the pot being sure it does not touch the bottom and the bulb is fully submerged into the syrup for an accurate reading.

Turn the heat to medium and allow the sugar to boil, undisturbed, until the temperature reaches 250°F (firm ball stage). This can take anywhere between 20-25 minutes depending on how your pot holds and distributes heat.

Slowly stir in the butter until fully melted, then stir in the peanuts until evenly incorporated.

Allow the mixture to cook and bubble, while stirring occasionally, until the temperature reaches 300°F-305°F (hard crack stage). This will take another 10-15 minutes. Remove from the heat immediately to stop the cooking.

Stir in the vanilla extract and baking soda until thoroughly combined. Be careful as the mixture will bubble up and get foamy when the baking soda is added.

Quickly pour the hot peanut brittle mixture onto the prepared baking sheet and spread to a thin (approximately ¼ inch thick), even layer using a silicone spatula. The brittle will harden quickly so you need to work fast to ensure an even thickness for the cooled brittle.

Allow the peanut brittle to cool completely at room temperature before removing the parchment paper and breaking into bite-sized pieces. Plate for serving immediately or add to a container for storage.