Mirror Glaze & Frosting

If you already have a mirror glaze recipe you love, you don't need to replace it. Make the glaze as usual and add the blue as it cools.

For a first test, try around 0.1 g blue spirulina per 100 g of glaze.

You'll need your usual white or pale mirror glaze, 0.1 g blue spirulina per 100 g glaze as a starting point, and a small amount of cool water for dispersing the powder.

Make your glaze as usual. Finish any boiling, melting or other high-temperature steps before worrying about the colour.

Mix the blue separately. Stir the blue spirulina into a very small amount of cool water until smooth.

Let the glaze cool. Once you're past the hottest part of the recipe, blend in the blue dispersion.

Check the colour. Add a little more if you want a deeper blue.

Glaze at the temperature your recipe requires. The glaze still needs to flow and set properly; don't wreck a good glaze just to keep the pigment a few degrees cooler.

That last point is important. The pastry comes first.

Blue spirulina is sensitive to heat, but that doesn't mean you should ignore the temperature your glaze actually needs to work.

White chocolate, vanilla, cream and pale sugar glazes give blue spirulina almost nothing to compete with.

That's how you get the ridiculous electric blue in the photograph.

An ivory base may give you a slightly different blue. A yellow buttercream will change it again. Put the same powder into caramel or chocolate and you're asking blue pigment to fight brown.

It will lose.

Buttercream doesn't have the heat problem of a cooked glaze.

For 500 g of pale buttercream, try around 0.5 g blue spirulina to begin with. Mix the powder into a tiny amount of water or another suitable liquid from your recipe first, then beat it through the frosting.

Want it deeper? Add more gradually.

The same idea works with many pale whipped toppings and cream-based finishes.

Don't dump a water dispersion straight into tempered chocolate and hope for the best. Water and chocolate have opinions about each other.

If you're colouring a white-chocolate ganache, mousse or glaze, the easiest route is usually to introduce the blue through the water-, milk- or cream-containing part of the recipe rather than directly into the chocolate itself.

For solid chocolate work, use a method developed specifically for that formulation.

You don't have to colour the entire dessert.

Blue-on-white marble: split the glaze and colour only one portion before loosely combining them.

Electric drip: keep the cake itself neutral and make the blue the finishing element.

Blue centre: use the colour in a mousse, cream or filling so it only appears when the dessert is cut.

Two-tone frosting: load blue and uncoloured buttercream into the same piping bag.

Full electric blue: or ignore subtlety completely.

That is also a perfectly respectable option.

This is where acidity is genuinely relevant, because berry, lemon and cultured-dairy pastry components can change the colour.

If you're adding blue spirulina directly to an acidic fruit glaze, curd or yogurt component, don't assume you'll get the same blue as you did in vanilla buttercream. Test a small amount in the finished component first.

But there's another solution: don't make every component blue.

A vivid blue exterior with a raspberry, lemon or passion-fruit centre gives you contrast in both colour and flavour without forcing the pigment into the most difficult part of the recipe.

Too pale? Make sure you're judging it in the actual finished glaze or frosting, then increase the dose gradually.

Greenish? Look at the natural colour and acidity of the base before reaching for more powder.

Dull after cooking? Next time, introduce the blue later in the process.

Speckled? Disperse it before adding it to the full mixture.

Beautiful glaze, ugly cake? Sadly outside the scope of this guide.

If you're working with cooked glazes, pastry creams or other hot components, we've gone into the heat part properly in the guide.