Gold Leaf Galaxy is accessible from the Engine Room observation dome. You need 34 Stars to enter.
It is a similar looking galaxy to the Honeyhive Galaxy. In fact the first planet is almost a mirror image of the first planet in Honeyhive.
Star 1: Star Bunnies on the Hunt
Look for the five bunnies around the initial planet. Close to each bunny is one of five blue star pieces to complete a jump star. Once active, the jump star leads you to another planet where you have to catch another bunny. It helps to ground pound the switch to elevate walls on this tiny planet so the bunny will be more easily cornered.
Star 2: Cataquack to the Skies
Lure the cataquacks to the circular launch pads with the cataquack emblems to launch yourself planet to planet. When you get to the area with the wood tower that looks like Jenga blocks, lure the cataquack to the green patch with the tiny shadow to launch yourself into a Bee Mario mushroom so you can fly up the tower with the cataquack's help.
Star 3: When It Rains, It Pours
With all the rainclouds scattering the area, Bee Mario is certainly in constant danger. Not to worry! Bee mushrooms are placed around the stage for when you need to get on the flowers or even on top of clouds.
Make it through the stage all the way up the tower to the boss in the pivoting tank that launches water balls. If a second player is at hand, they can make themselves useful by popping the water balls before Mario gets hit. Ground pound the red switch in the back to elevate panels in front of the boss for a short time. Jump on the moving platforms over to the panels and jump up to ground pound the boss. Repeat this process 3 times for victory.
Star 4 (Cosmic Comet): Cosmic Mario Forest Race
It's like the Cosmic Race on Honeyhive Galaxy, but you will have to go up the platforms and catch the star on the second wood circle. High jumps and cosmic Mario movements may help.
Star 5 (Purple Comet): Purple Coins in the Woods
Find 100 Purple Coins in 3:30. Check with the bees – if a bee says you need to have 50 coins and you have 47 coins, you have to go back and find the remaining three coins you missed, which costs time.
Star 6 (Hidden): The Bell on the Big Tree
Enter Star 2 as directed. Follow walkthrough until the first cataquack flings you. By the big tree, jump into a bubble. Hit the bell with the pointer (not with Mario), then collect all the musical notes to make the Star appear.