Wash the strawberries, cut off the stem, and cut them into small pieces.

In a medium pot, add the strawberries and the sugar. Cook on medium for 10 minutes or until it bubbles.

Reduce the heat to medium-low and cook for another 15 minutes, stirring occasionally.

Using a potato masher, mash the fruit down, or using an immersion blender, purée them. Set aside until the strawberry puree is completely cooled down.

In a bowl, using a hand mixer, whisk the egg white until stiff peaks form. Set aside.

In another bowl, large, using your hand mixer or stand mixer, whip the heavy cream until you obtain stiff peaks.

Take the strawberry purée, set about 6 to 8 tablespoons aside, and now you can delicately fold it into the stiffed egg white with a rubber spatula. The gesture should go from the back of the bowl to the bottom and come up from the front and repeat gently until fully incorporated. This will keep the egg whites light and airy.

Lastly, mix the strawberry mixture into the whipped cream. Similar to the previous step, you should be gentle when merging these 2 and use again the rubber spatula.

Assembling: Scoop a tablespoon of strawberry purée at the bottom of each jar and pipe (if you wish) or scoop the mousse to the top. Decorate with a fresh strawberry and refrigerate for 2 hours.