In a medium-size pot combine blueberries(18oz, 500grams) with sugar (1/2 cup, 100grams) and lemon juice (juice of one medium lemon). Bring to boil and reduce to simmer and cook until very soft and juicy.

Remove from the heat and process in a small food processor or use an immersion blender to puree fruit until smooth.

Strain blueberry puree thru a fine-mesh sieve to remove the seeds. Set aside.

Measure generous 1 cup of fruit puree into a mixing bowl.

Into a heatproof mixing bowl (tempered glass or stainless steel bowl) pour 3 egg whites, and add granulated sugar (1/2 cup) and cream of tartar (1/4 teaspoon) or some lemon juice/vinegar (1/2 teaspoon). Whisk to combine the ingredients.

Place the bowl over the pot with simmering water. Stirring constantly, bring the mixture over 160F, about 5 minutes

Remove from the heat and beat with a handheld mixer or with a stand mixer on medium-high to medium peaks.

TIP: Don't know what to do with 3 leftover egg yolks? Try making my delicious tart cookie dough, it's perfect for cookies and tart crusts. Recipe link in the notes

Depending on the type of gelatin you are using here are the instructions for both, granulated and sheet gelatin.

1. Granulated Gelatin

Into a small dish pour 1/4 cup cold water, and sprinkle gelatin (2tsp) evenly over the top of the water while whisking with a fork. Set aside for 5 minutes. Gelatin will swell up (bloom). It will be spongy. Then microwave it on high in 3 seconds intervals, stirring well after each period, until dissolved. It will only take several seconds. Don't overheat it. Continue with the next step - Prepare Blueberry Mousse Mixture.

2. Sheet Gelatin

Pour 3 cups of cold water into a bowl. Add gelatin sheets (3 sheets, 230-250 bloom), and soak them, until soft, for about 5-10 minutes. Then remove the soft sheets from the water and squeeze out the excess water. Continue with the next step - Prepare Blueberry Mousse Mixture.

TIP: Don't use boiling water as it will destroy the gelatin setting agent.

Into a bowl pour whipping cream/heavy cream. Beat until medium-soft peaks are formed.

1. Blueberry Puree and Gelatin

Into a bowl pour blueberry puree (generous 1 cup), if the puree is cold heat it up till it's warm, but not boiling hot. Pour in prepared dissolved gelatin/soften gelatin sheets (follow the previous step to prepare gelatin). Stir well to combine.

2. Add Meringue

Into the blueberry puree mixed with dissolved gelatin fold meringue, in 3 additions. It's okay if the meringue is slightly warm.

3. Add Whipped Cream

When adding chilled whipped cream, "temper" the blueberry mixture by adding only about 1/2 cup of whipped cream. At this point, you can fold whipped cream into the blueberry mixture more vigorously. Then continue folding medium-soft peaks into the blueberry mixture.

Divide blueberry mousse into serving dishes. Allow the mousse to set in the fridge, for at least 4 hours and ideally overnight. Blueberry mousse will last in the fridge for up to 5 days.