It's difficult to get moles out of a garden, but testing has shown the most effective methods are kill traps and poison baits. Castor oil solutions applied in the environment encourage them to move elsewhere, but must be re-applied every couple of weeks and after heavy rains. Below are links to two pretty thorough articles on mole control. They are not in complete agreement, but provide good descriptions of the recommended options. Don't apply grub control products unless you actually see grubs. Moles also like healthy, grub-free garden beds because of the abundance of earthworms they contain.
These articles also describe the difference between moles and voles. It's a good idea to confirm the pest, so that habitat modifications can be made, if appropriate.
The yellow substance is most likely a slime mold, commonly referred to as "dog vomit fungus". Please confirm by looking at the photos in at the links below. It grows on decaying wood--the mulch--thriving when conditions are right. Though unsightly, it's harmless. To remove it, simply lift it off the mulch by sliding a shovel or similar implement underneath it and discarding it in the trash. Here are some photos: