Make the topping: In a large bowl combine the brown sugar, egg, and salt. Beat with an electric mixer at high speed until thick, about 5 minutes. Stir in the chocolate chips, nuts, and vanilla extract.
Preheat oven to 375 degrees F. Insert liners into a medium cupcake pan.
Combine the butter, sugars, and vanilla in a small bowl. Beat with an electric mixer on medium speed until creamy. Add the egg and beat for 1 minute.
In a separate bowl combine the flour, baking soda, and salt.
Gradually add the dry ingredients to the egg mixture and mix with a rubber spatula or wooden spoon until fully integrated.
Fill the cupcake liners 1/2 full. Bake for 15 minutes. Remove from the oven. Turn up the oven temperature to 425 degrees F. Spoon 2 tablespoons of topping over each cupcake. Return the pan to the oven. Bake for 10 more minutes. Cool cupcakes in the pan.
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