We like the tart flavor of McIntosh apples in this recipe, but Jonagold and Pink Lady apples are good, too. Nearly any variety of apple can be substituted, except for Red or Golden Delicious. You may mash this applesauce until it's smooth or leave it chunky for a more rustic effect. Serve with roast pork, turkey, or duck.
1. Bring reserved peels and cores and 1 cup water to boil in small saucepan over medium-high heat. Reduce heat to medium, cover, and cook, mashing occasionally with potato masher, until mixture is deep pink and cores have broken down, about 15 minutes.
2. While peels and cores cook, cut apples into quarters and place in large saucepan. Add parsnips, sugar, ¼ teaspoon salt, cayenne, and remaining ½ cup water and bring to boil over medium-high heat. Reduce heat to medium, cover, and cook, stirring occasionally with rubber spatula, until all apples are soft and about half are completely broken down, about 15 minutes. (Parsnips will not completely soften.) Using potato masher, mash apple mixture to desired consistency.
3. Transfer peel-and-core mixture to fine-mesh strainer set over saucepan of mashed apple mixture. Using rubber spatula, stir and press peel-and-core mixture to extract pulp; discard solids. Stir in mustard. Season with salt to taste. Serve warm or at room temperature. (Applesauce can be refrigerated for up to 1 week.)