Attach a candy thermometer to a large, heavy-bottomed saucepan.
Bring maple syrup to a boil in the saucepan over medium-high heat, stirring occasionally, until syrup reaches 235 degrees F (110 degrees C).
Remove from heat and cool to 175 degrees F (80 degrees C) without stirring, about 10 minutes.
Stir mixture rapidly with a wooden spoon until thick, creamy, and lighter in color, about 5 minutes.
Stir in chopped nuts.
Pour into molds; allow to cool at room temperature until set.
Unmold candy. Store in an airtight container for up to 1 month.