Prepare the Fudge Base:

1. Combine Ingredients: In a 3-quart stainless steel pot, mix milk, brown sugar, white sugar, salt, and chopped dark chocolate.

2. Cook the Mixture: Place the pot over medium heat and stir constantly until the chocolate melts and the mixture becomes smooth. Continue stirring until the mixture starts bubbling (about 6 minutes). Once bubbling, stop stirring.

3. Clean the Sides: Use a pastry brush dipped in water to clean the pot’s sides, removing sugar crystals or chocolate splashes. Repeat during cooking.

4. Monitor the Temperature: Attach a candy thermometer to the pot and cook the syrup until it reaches 236°F (around 6 minutes). The syrup should bubble actively but stay contained.

5. Cool the Mixture: Remove from heat once it reaches 236°F and let it cool undisturbed to 115°F (about 1 hour). Some chocolate flecks may form on the sides.

Whip the Frosting:

1. Transfer to Mixer: After the mixture cools to 115°F, transfer it to the stand mixer bowl.

2. Add Vanilla Extract: Mix on low to incorporate the vanilla extract.

3. Mix Until Thick and Creamy: Gradually increase the speed to medium and mix for about 10 minutes until thick and creamy.

4. Continue Beating: Reduce speed to medium-low and mix for another 5 minutes until the frosting cools to 78°F.

5. Add Butter: Gradually add softened butter one tablespoon at a time. Mix well before adding more butter.

6. Scrape the Bowl: Once all butter is incorporated, scrape the bowl with a spatula.

7. Let It Rest: Cover the frosting and let it rest at room temperature for about 30 minutes to set. For best results, let it rest for up to 12 hours before using.

Use the Frosting:

• After resting, the frosting is ready to be spread or piped onto cakes, cupcakes, or other desserts.