Add the pecan halves to a food processor. Pulse a few times, then grind on low until coarse.

Whisk together condensed milk, flour, and vanilla extract in a saucepan over medium heat until fully combined.

Stir ground pecans into the warm mixture; cook for 8 to 10 minutes until thickened.

Pour mixture into a 9x9 dish, cover, and chill for 20 minutes.

Line a baking sheet with parchment paper.

Use a 1 tablespoon scoop to form the pecan balls.

Dampen hands and roll mixture into balls.

Chill balls for 20 minutes.

Melt chocolate in microwave at 30-second intervals, stirring after each.

Dip each ball into melted chocolate and shake off excess.

Garnish with chopped pecans if desired.

Return to refrigerator for 20 minutes before serving.