Add potatoes to a large stockpot. Bring to a boil, then lower to a simmer and cook until tender, about 25-30 minutes.
While the potatoes are cooking, whisk together chicken broth, milk, mascarpone cheese, butter and dash of cayenne pepper in a bowl, large enough to accommodate the potatoes as well. Add salt & pepper to taste.
Once potatoes are cooked, drain water. Use a hand mixer on medium speed to whip potatoes until fluffy; a few lumps will be present and thats ok.
By hand fold in mascarpone mixture with potatoes. Stir well. Taste and add a little more salt, if desired.
Evenly spread mashed potatoes into a 9x13-inch baking dish. Using the edge of your rubber spatula to gently press and lift up to create little pretty peaks. Bake uncovered in oven until potatoes are heated through and peeks are beautiful golden brown, about 25 minutes.
These potatoes can be prepared ahead of time and stored in the refrigerator for up to 48 hours before baking.