Preheat oven to 180C (350F).

Grease an 8-inch square shallow pan.

Melt butter and chocolate together in a heatproof bowl over a pan of simmering water or in the microwave.

Remove from heat when the chocolate has melted completely.

Beat in the sugar, eggs, and vanilla extract until well combined.

Stir in the flour, orange zest, chopped apricots, and chopped walnuts until just combined. Do not overmix.

Pour the batter into the prepared pan.

Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean and the surface is lightly cracked.

Let it cool in the pan for 5-10 minutes before cutting into squares and serving.