Preheat oven to 350°F. Line cupcake pans or grease and parchment-line 8-inch cake pans.
Add cake mix, milk, eggs, oil, sour cream, vanilla, and salt to a large bowl. Whisk or mix on low speed just until fully blended, about 45 to 60 seconds. Scrape down the bowl once, then mix another 10 seconds only. Do not overmix. Batter should look thick and silky.
Fill each tin 1/3 of the way with batter. Should make 6-8 cakes. Bake for 17-19 minutes to start. Start checking at 15 min. Cakes are done when a toothpick inserted into the center comes out with a few moist crumbs. Do not wait for a totally clean toothpick or the cake may overbake. Let them cool completely.
Fill each cake tin with softened ice cream reaching 2/3 of the way up. We need to leave room for the fudge. Once you have ice cream in each tin, refreeze at least 8 hours.
Top each cake with 1/4 cup fudge frosting. Spread evenly over the top of the cake. Sprinkle a handful onto each cake. Serve right away. If you need to refreeze, be sure to take them out a few minutes before serving.
When you refreeze them, use the lids that come with the tins to keep the cakes fresh.