Found this recipe,
It should work out ok. 15 minutes may not be enough time depending on the quantity. Make sure the bag can withstand boiling water. I know the vacuum seal ones can but have heard of Ziplocs failing in boiling water.
You could just take your Anova and a smaller pot/stockpot to your friends house. That way you could plug it in away from the busy kitchen stove and not worry about boiling water.
I tried this recipe myself. 194°F. Peeled and sliced thin Russet potatoes. Excellent. I recommend reheating at a relatively high temperature, say about 155°F to “reinvigorate” the starches in the taters. Leave them in the bag to be reheated. Drain the liquid after reheating and save it to be reincorporated into the mashed potatoes. Mash by hand or a potato ricer. Be gentle. don’t use a blender this time.