Preheat oven to 275°F. Prepare a baking sheet with parchment paper and set aside.
In a large (squeaky clean) mixing bowl, whisk egg whites on medium speed until foamy.
Add cream of tartar and salt and whisk on medium speed until soft peaks form.
Add sugar slowly with the mixer running (about a tablespoon at a time) on high speed until stiff peaks form.
Fit a piping bag with desired tip and fill with meringue.
Pipe onto prepared baking sheet: Starting in the middle, pipe in a circle to create a base and then pipe another layer or two up the sides, creating a little crater in the middle.
Place meringues in the oven and immediately turn down to 225°F. Bake for 1 hour (or until meringues are dry to the touch, but not yet golden - you want them to stay white) and crack open the oven door. Leave the meringues in the oven to cool completely, for at least a few hours or even overnight.
Zest a lemon and set the zest aside. Slice the lemon in half an juice it to get approximately 1 to 1 ½ tablespoons of juice.
In a small saucepan, combine blueberries, lemon juice and sugar and simmer over medium heat until boiling, then reduce the heat and simmer. Stir frequently and let it simmer until the sauce has thickened and it takes a second or two for the sauce to re-flood the area you just dragged your spoon through.
Remove from heat and place a mesh strainer over a small bowl and press the sauce through the strainer. You'll end up with around a tablespoon of jam - set it aside and save it for breakfast!
Let the strained blueberry syrup cool completely.
While the blueberry sauce is cooling, chill a medium mixing bowl in the fridge.
In your chilled bowl with a whisk attachment, combine mascarpone cheese and sugar on a high speed until completely combined.
Add lemon extract and heavy cream, and mix on a low setting until it is mostly combined. Now increase speed to high and whip until stiff peaks form.
Add cooled blueberry sauce and whip again to combine.
Fit a piping bag with desired tip and fill your cooled meringues.
Top with reserved lemon zest and mini robin eggs candies and serve immediately. Enjoy!