2 cups pecan halves plus 24 for garnish
1 cup sugar
1 cup (packed) light brown sugar
½ cup pareve whipping cream
2 tablespoons (1/4 stick) margarine
4 ounces semisweet or bittersweet chocolate, melted
Line 2 baking sheets with parchment.
In a medium saucepan combine 2 cups pecans, both sugars, cream and margarine over medium-high heat. Stir often. Attach candy thermometer to side of pan. Boil, occasionally swirling pan, until thermometer registers 236°F, 7-8 minutes.
Remove from heat; stir vigorously with a wooden spoon until mixture thickens and pecans are suspended in syrup, 2 – 3 minutes.
Drop candy by heaping teaspoonfuls onto prepared sheets. Let cool completely. Spoon some melted chocolate over; place a pecan half on top. Chill until set, about 30 minutes.
Do Ahead: Can be made 1 week ahead. Store airtight in refrigerator. Return to room temperature before serving.