In a saucepan, combine the brown sugar, cream, sugar, maple syrup, butter and salt and bring to a boil, stirring with a wooden spoon to dissolve the sugar. Attach a candy thermometer in the center of the pan and simmer over medium heat without stirring until the thermometer reads 237 degrees F (114 degrees C). Add the vanilla extract without stirring.
Place the pan in a cold water bath. Cool, without stirring, until the thermometer reads 113 degrees F (45 degrees C), about 20 minutes.
Remove the pan from the water bath. Using an electric mixer or a wooden spoon, stir vigorously until the mixture begins to lighten in color and become creamy, 2 to 3 minutes. Please note that if you whip too much, the sugar and cream mixture will harden before you have time to pour it into the pan.
Pour immediately into the prepared pan and smooth with a spatula. Garnish with crushed toasted pecans and Maldon salt. Cover with plastic wrap. Let cool for about 1 hour at room temperature or 30 minutes in the refrigerator. Remove from the pan and remove from the plastic wrap. Cut into squares. Store in an airtight container.