Bring the maple syrup to a boil in a small saucepan over medium heat. Remove the saucepan from the heat.
To a bowl containing the egg yolks, slowly add a few spoonfuls of the boiled syrup while whisking constantly (this is to temper the eggs). Then add the tempered egg mixture to the saucepan, whisking constantly to heat through without cooking the egg yolks. Set aside for later.
Pour the skim milk into a small heatproof bowl and sprinkle the gelatin on top. Let stand for 5 minutes to bloom.
Place the bowl of bloomed gelatin over a pan of simmering water and gently heat to dissolve. Add the dissolved gelatin mixture to the syrupy-egg mixture and stir to combine. Set aside.
Whip the cream to stiff peaks, then take a few scoops of the whipped cream and add it to the syrupy-egg mixture (to lighten it before mixing with the cream). Now add that lightened syrupy-egg mixture to the whipped cream, and fold to combine. Don’t worry if you have to be a little rough. You want the mousse mix to be smooth and light.
Chill for 1.5 hours until set enough to pipe into your edible cookie cups.