Step 1

Preheat oven to 180°C. Grease a 3cm-deep, 17cm x 28cm (base) slab pan and line with baking paper (see note).

Step 2

Combine Nuttelex and 1/2 cup choc bits in a heatproof, microwave-safe bowl. Microwave, uncovered, on MEDIUM (50%) for 2 to 3 minutes, stirring every minute with a metal spoon, or until smooth. Stir in sugar and eggs.

Step 3

Stir flours, cocoa and xanthum gum over chocolate mixture. Add remaining 1/2 cup choc bits. Stir gently to combine.

Step 4

Spread mixture into pan. Bake slice for 22 to 25 minutes or until a skewer inserted into the centre comes out clean. Cool completely in pan.

Step 5

Dust slice with chocolate. Cut into pieces. Serve.