To unlock the new chain Varmint Cannon goals, you need to buy the Cannon Quest from the Market for 4,750 Coins. The goals will require you to build the Foundry as well as the four types of Varmint Cannons.
As stated above, Part 1 of the Varmint Cannon Goals is Build a Foundry. This goal requires you to get one Saltpeter, craft one Fire, and finally build your own Foundry.
The Saltpeter is acquired by completing the Manure Collection. This is an important item because you’ll need lots of Saltpeter to use the Varmint Cannons. Fire is crafted inside the Covered Wagon. The Foundry is found in the Market.
You have to whack it 25 times with each whack at 10 Wood. Then you need to collect five Shingles, five Mallets, five Pegs, five Cements, and five Windows. Once you’ve completed the Foundry, you’ll be rewarded 35 XP.
Once you’ve completed the Build a Foundry goal, you’ll receive 100 XP and 500 Coins.