Line a large rimmed baking sheet with foil and generously butter it. Working in batches, cook the bacon in a large skillet over medium heat, turning occasionally, until crisp, 9 to 11 minutes. Drain on paper towels, then break each slice in half.
Combine the sugar, corn syrup and 1/2 cup water in a medium heavy-bottomed saucepan. Cook, stirring occasionally, over medium-high heat until a candy thermometer registers 260 degrees F, 10 to 12 minutes.
Remove from the heat and add the butter, nuts and 1 teaspoon salt. Stir once, then continue cooking over medium-high heat, undisturbed, until the syrup turns golden and the candy thermometer registers 285 degrees F, 5 to 10 more minutes. Carefully stir in the prepared bacon, the vanilla and baking soda. (The mixture will foam a bit.) Cook, stirring several times, until the foam subsides and the mixture darkens slightly, 1 to 2 more minutes.
Pour the mixture onto the prepared baking sheet, then carefully tilt to spread it into a thin layer. Use tongs to redistribute the bacon pieces if necessary. Let cool completely, then break into pieces.