How to Make It
Preheat oven to 350°F. Place dates, tea bags, and baking soda in a medium bowl. Add 1 1/4 cups boiling water, and let stand 15 minutes. Remove and discard tea bags. Stir mixture with a fork to break apart dates.
Stir together flour, baking powder, and 3/4 teaspoon salt in a medium bowl; set aside. Combine shortening, 1/4 cup light muscovado sugar, and 1/4 cup dark muscovado sugar in the bowl of a stand mixer. Beat on medium speed until no lumps remain, about 1 minute. Add eggs, 1 at a time, beating well after each addition. With mixer running on low speed, gradually add flour mixture just until incorporated. Stir in date mixture. Lightly grease a 9-inch square baking pan with butter. Pour batter into prepared pan, and bake in preheated oven until a wooden pick inserted in center of pudding comes out clean, 30 to 32 minutes.
Remove pudding from oven, and immediately prick all over with a wooden or metal skewer, piercing all the way to the bottom of pan. Pour 1 1/2 cups warm toffee sauce evenly over pudding, and let stand until sauce is absorbed, about 30 minutes. Cut warm pudding into 9 (3-inch) squares. Top servings with ice cream or clotted cream; drizzle evenly with remaining 1/2 cup toffee sauce.