In a heavy saucepan, combine Splenda Sugar Blend, corn syrup, water, and butter. Cook over medium-high heat, stirring constantly, until sweetener dissolves and mixture begins to boil.
Reduce temperature to medium-low; cook, stirring occasionally, until candy thermometer reaches 275°F (about 20 minutes).
Add peanuts and continue cooking until candy thermometer reaches 295°F (about 10 minutes).
Remove from heat and quickly sprinkle baking soda over mixture, stirring until blended.
Pour into prepared pan or marble slab, spreading thinly.
Cool completely before breaking into bite-size pieces.