Place the thawed mango chunks in a food processor or high powered blender, and pulse until a smooth puree forms. Add the egg yolks, one at a time, pulsing until they’re well combined. Set the mixture aside.
In the bowl of a stand mixer, beat the egg whites on medium speed until foamy. Add the cream of tartar, and continue beating until soft peaks form. Pour in ¼ cup of sugar and beat until stiff peaks form (the egg whites should be able to stand upright in peaks). Using a spatula, gently fold the egg whites into mango puree mixture.
Use the bowl of the stand mixer a second time to mix the remaining 1 tablespoon of sugar, heavy cream, and vanilla. Mix on medium speed until stiff peaks form. Gently fold the whipped cream into the mango mixture.
Divide the mousse evenly between 6 serving glasses. Cover and chill for at least 2 hours or up to overnight. If desired, make additional whipped cream for serving.