Line a large heavy baking sheet with parchment paper or aluminum foil and set aside.
Combine the sugars, heavy cream, and butter in a large heavy saucepan and cook over medium-high heat, stirring, until the sugars have dissolved, about 3 minutes. Continue to cook until the mixture reaches the softball stage, 238 to 240 degrees F on a candy thermometer, 3 to 4 minutes.
Remove from the heat, add the pecans and chocolate chips, and stir vigorously until the pecans remain suspended in the mixture, about 2 minutes. Spoon onto the prepared baking sheet, spreading with the back of the spoon to form a thin layer of uniform thickness. Cool completely and then crumble, as needed. (Alternatively, make individual pralines by dropping the hot praline mixture by the spoonful onto the prepared baking sheet, let cool, and then remove with a thin knife.)
Yield: about 3 cups crumbled pralines