In a small saucepan, bring the half and half and vanilla to a boil, then remove from the heat.
In a medium sized bowl, whisk the egg yolks and sugar, then whisk in the flour.
Add the boiled half and half to the egg yolk mixture and whisk together, then return to the saucepan.
Bring the custard to a boil again, whisking as it thickens. Boil for 10 seconds then remove from the heat.
When you're ready to serve, spoon the custard into four dessert dishes (or margarita glasses!). Arrange the sliced strawberries around the outside. If you have raspberries add them to the center.
If the jam is thick, heat for about 10 seconds in a microwave so it's pourable, then drizzle over the berries.