This is a variation on the technique Cook's Illustrated uses for making mashed sweet potatoes. I've used half sweet potatoes and half parsnips. To add some dimension I've incorporated freshly grated horseradish root. I've cooked part of the horseradish root with the vegetables to soften it's pungency plus stirred some in after cooking for added pizzazz. I find the combination to be sweet with enough of a bite to add interest, but not clear the sinuses! If you don't find it to be sweet enough, add a small amount of sweetener. Feel free to adjust the pungency to your taste with additional horseradish. —hardlikearmour
Test Kitchen Notes
I'm always a fan of recipes that only dirty one dish from start to finish. The parsnips are wonderful with the sweet potatoes. The kick of horseradish adds something special to the dish and a tablespoon of maple syrup made it complete. - biffbourgeois —Stephanie Bourgeois
Peel sweet potatoes and parsnips, and cut into 1/4-inch thick slices.
Combine sweet potato and parsnip slices, cream, butter, salt, and half of the horseradish root in a 3 or 4 quart saucepan with a tight fitting lid. Heat over low heat, stirring occasionally, until vegetables have softened. This will take about 40 to 50 minutes.
Remove from heat and mash with a potato masher to desired texture. Stir in half of remaining horseradish making sure to incorporate well. Taste and adjust seasoning with salt, additional horseradish, and/or sweetener if needed. Serve hot.