Place all the filling ingredients (except for the mascarpone and strawberry syrup) in a heatproof bowl over a saucepan of boiling water. Reduce the heat to medium-low. Whisk continuously until the mixture doubles and has a thick and creamy consistency (about 10 to 15 minutes). Remove from the heat and set aside to cool completely.
Meanwhile, beat the whipping cream with the strawberry syrup with an electric handheld mixer until it’s about 70% done (soft peaks). Set aside.
In another large mixing bowl, whisk together the mascarpone, strawberry syrup, and the egg mixture (which has cooled completely!). Gently fold in the strawberry cream two separate times.