Combine the brown sugar, milk, salt, butter, peanut butter, and cocoa in a large saucepan over medium-high heat. Stir to dissolve as the mixture heats. Continue to cook, stirring, until the mixture begins to bubble around the edges of the pan and reaches 234° to 240°F on a candy thermometer, or the soft ball stage (that is, when a bit of the mixture is dropped into cold water, it forms a soft ball that flattens), about 12 minutes.
Remove from the heat and stir in the pecans. Drop the mixture by the tablespoonful onto waxed or parchment paper on a baking sheet and let cool completely. Lift the pralines off the paper with a thin knife.
Pralines can be stored in an airtight container at room temperature for up to 2 weeks.
Yield: about 1 1/2 dozen pralines