===== Brownies =====
Mash bananas heavily in large mixing bowl.
Stir beaten eggs into bananas.
Add sugar, sour cream, butter (or margarine), vanilla, baking soda, and flour and mix until all ingredients are combined well.

Grease a 13x18 deep baking dish with pam or equivalent. Dust with flour. Pour mixture carefully, attempting to cover entire pan. Use a spreader to evenly coat the pan. Allow to settle for 5 minutes.

Bake at 375℉ for 20-25 minutes (toothpick stuck in the middle should come out clean).

===== Frosting =====
Start frosting with about 15 minutes left on the timer.

On medium heat, melt butter in small saucepan. Continue to stir butter until browned.
Add milk and vanilla to butter then slowly stir in powdered sugar until all ingredients are melted and combined. Keep warm, but do not overcook.

Pour frosting over brownies as soon as they come out of the oven. Spread evenly. Allow to cool 5-10 minutes before cutting and serving.

To make the babka, it takes 30 minutes of hands-on time, and then 45 minutes to bake. So you’ll need to set aside a good hour and a half to create the GBBO recipe. Prepare yourselves, as there’s quite a few steps involved!

Step 1: Heat the oven to 200°C/180°C fan/Gas 6.

Step 2: Make the filling. Tip the hazelnuts into a baking tray and roast in the bottom of the oven for 4–5 minutes, tossing occasionally, until light golden. Tip onto a chopping board, leave to cool, then roughly chop half the hazelnuts and finely chop the remainder. Set aside.

Step 3: Place the butter, sugar and chocolate in a pan and melt very slowly over a low heat, stirring until smooth and combined. Remove from the heat and stir in the cocoa powder. Pour into a bowl and leave to cool and thicken slightly.

Step 4: Meanwhile, make the dough. Tip the flour into the bowl of a stand mixer fitted with the dough hook, add the yeast to one side of the bowl and the sugar and salt to the other side.

Step 5: Make a well in the centre and pour in the eggs and milk, then mix on slow speed for 2–3 minutes, until firm.

Step 6: Increase the speed to medium and add the butter, a little at a time. Mix well between each addition, allowing the butter to incorporate before adding more.

Step 7: Once you have added all the butter, continue kneading with the dough hook on medium speed through the sticky stage, until you have a ball of smooth, silky, shiny dough.

Step 8: Lightly flour a work surface and roll out the dough to a 40 x 30cm rectangle, with a long edge closest to you.

Step 9: Spread the cooled chocolate mixture over the dough, leaving a 1cm border all around. Sprinkle all the toasted hazelnuts over the top.

Step 10: Starting from the long edge closest to you, roll up the dough into a tight spiral, with the seam underneath.

Step 11: Trim about 2cm off each end to neaten, then turn the roll through 90° clockwise so that a short end is closest to you. Using a large, sharp knife or a pizza cutter, slice lengthways, down through the middle of the dough, cutting it into 2 long pieces.

Step 12: With the cut-sides facing upwards, gently press the top end of each half together to seal, then lift the right half over the left half, followed by the left half over the right half. Repeat, twisting the dough to make a two-stranded plait, then gently press the bottom ends together to seal.

Step 13: Carefully lift the loaf into the lined tin and cover with a clean tea towel (or place in a proving bag, if you have one). Leave at room temperature for about 2 hours (or in a proving drawer for 1 hour), until doubled in size.

Step 14: Fifteen minutes before the end of the proving time, heat the oven to 190°C/170°C fan/Gas 5.

Step 15: When the babka has proved, bake it for 15 minutes, then reduce the oven temperature to 170°C/150°C fan/Gas 3 and cook for a further 25–30 minutes, until a skewer inserted into the centre comes out clean.

Step 16: While the babka is baking, make the syrup. Tip the sugar and 100ml water into a small pan, bring to the boil over a medium heat, stirring until the sugar dissolves. Reduce the heat and simmer, without stirring, for 5 minutes, until syrupy. Leave to cool.

Step 17: When the babka is ready, transfer it in the tin to a wire rack. Brush the cooled syrup over the hot babka, then leave in the tin until warm enough to handle. Turn out onto the wire rack and serve warm or at room temperature.