Heat the oven to 350 degrees F and position a rack in the center, then butter and flour a 10-inch bundt pan thoroughly. The pan should look evenly coated in every groove so the cake can release cleanly later.
Add the carrots, eggs, sugar, oil, and salt to a blender and process until the mixture is very smooth, then pour it into a large bowl and whisk in the sifted flour and baking powder by hand. The blended base should fall in a thick ribbon and look uniformly orange, with no dry streaks left once the flour is mixed in.
Transfer the batter to the prepared pan and bake for about 50 minutes. The cake is ready when a toothpick inserted in the center comes out clean and the top sounds lightly hollow when tapped.
Set the pan on a rack and cool the cake for 10 minutes, then run a butter knife around the edges, tap the pan firmly, give it a gentle shake, and invert onto a cooling rack. If the cake is ready to release, you'll feel it loosen slightly before it drops out.
For the brigadeiro, cook the chocolate, sweet condensed milk, and butter in a saucepan over medium-low heat, stirring constantly, until thickened and the mixture briefly exposes the bottom of the pan, about 10 minutes, then stir in the heavy cream until smooth. The finished glaze should look glossy and thick enough to coat a spoon but still flow easily when poured.
Move the cooled cake to a serving platter, pour the brigadeiro over the top, and finish with chocolate sprinkles if desired. Let the glaze settle for a few minutes so it clings to the cake instead of running straight off.