Ingredients:

4 large sweet potatoes (or the equivalent)
zest of two lemons
juice of two lemons
1/2 cup butter, softened
2 egg yolks
1/2 teaspoon salt

Instructions:

Boil sweet potatoes in water until tender (check at about 7-10 minutes, will depend on size of potatoes)
Once tender, drain potatoes and rinse with cool water
Use towel or pot holder to peel skin off sweet potatoes
Place in bowl and mash with butter, lemon juice, lemon zest, egg yolks and salt
If desired, whip with electric mixer
Transfer mixture to buttered ovenproof casserole dish
Bake at 350F for 30 minutes