Prepare cake batter according to package directions, adding lemon extract. Pour into a greased and floured 9-in. round baking pan.
Bake at 350*F. for 25 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.
In a bowl, whisk milk and pudding mix for 2 minutes; refrigerate. Ina heavy saucepan or microwave; melt chocolate and butter, stir until smooth. Stir in confectioners' sugar until crumbly. Stir in hot water, 1 teaspoon at a time, until smooth. Split cake into two horizontal layers. Spread pudding on bottom layer. Place second layer over pudding. Pour chocolate glaze over top, letting it drizzle down the sides. Store in the refrigerator.
My Notes: Some time I didn't have a box mix so I made a yellow cake from scratch! It was wonderful! Using one cup of milk in pudding is CRUICIAL! As is letting the pudding and cake cool completely. The pudding turns stiff, kinda like Mousse or Flan. That makes it PERFECT for spreading between layers.
I used less milk in the pudding (1cup) might try 1&1/2c. next time. Chilled the pudding first and the cakes before putting together. I also sliced the rounded top off the bottom cake so pudding would sit nicely. French vanilla instant pudding gives it the custard effect. Extremely easy.
I used French Vanilla cake mix and pudding because that's what I had. I also used only 1Cup milk - I think I could have used 1 1/4 and had a little more pudding, but it worked out fine. The key is to make sure EVERYTHING is cool. I put the cake and pudding in the fridge before assembling. With the cake cold the icing cooled quickly and set easily on the cake instead of just drizzling off the cake and onto the pan.