Preheat your oven to 170 degrees C (150 degrees C fan). Line an 8x8 inch baking tin with parchment paper, allowing the edges to hang over for easy removal.

Melt the white chocolate and butter together in a saucepan over low heat or in a bowl set over simmering water, stirring until the mixture flows smoothly. Allow it to cool slightly and set aside.

In a bowl, beat the eggs and granulated sugar together until light and fluffy.

Gradually fold the melted white chocolate mixture into the egg and sugar blend.

Sift in the plain flour and salt, gently folding until no dry streaks remain.

Pour the batter into the prepared tin, spreading it evenly.

Bake for 20 minutes, or until the edges are light brown and the surface crackles.

Allow the blondies to cool completely in the tin before adding the ganache.

Melt the remaining white chocolate with double cream over low heat, stirring until smooth and glossy.

Pour the ganache over the cooled blondies, spreading it into an even layer.

Sprinkle with rainbow chocolate drops.

Refrigerate the blondies to set the ganache thoroughly.

Cut into squares and serve.