In a large saucepan combine the water, dates, and pears. Bring to boiling; reduce heat. Cook, covered, about 15 minutes or until fruit is tender and most of the liquid is absorbed. Mash with a potato masher, fork, or immersion blender until as smooth as possible. Stir in baking soda; set aside.
Preheat oven to 350 degrees F. Grease an 8x8x2-inch baking pan; set aside. In a small bowl combine flour, baking powder, salt, and nutmeg; set aside. In a large bowl combine brown sugar and butter. Beat with an electric mixer on medium speed about 1 minute or until combined. Beat in eggs, one at a time, and vanilla. Stir in date-pear mixture. Stir in flour mixture just until combined. Pour batter into prepared baking pan.
Bake in the preheated oven for 40 to 45 minutes or until a toothpick inserted near the center comes out clean. Place pan on a wire rack. Immediately use a long skewer to prick top of cake all over. Spoon the portion of Toffee-Pear Sauce without pears over cake. Bake for 3 minutes more. Cool on the wire rack for 10 minutes. Serve warm with the portion of Toffee-Pear Sauce with pears.
Peel and core pear; thinly slice pear. In a medium skillet melt 1 tablespoon butter over medium heat. Add pear slices; cook for 2 to 3 minutes or until tender and lightly browned, turning pear slices occasionally and reducing heat to low if pear browns too quickly. Set aside. In a small saucepan melt 1/2 cup butter over medium heat. Stir in brown sugar. Bring to boiling, stirring until sugar dissolves. Boil gently, uncovered, for 5 minutes, stirring occasionally. Carefully stir in whipping cream. Bring to boiling. Remove from heat; stir in vanilla. Divide sauce in half. Stir pear slices into one portion.