Preheat oven to 325°F. In small bowl, whisk egg yolks and vanilla extract until smooth. In saucepan over medium heat, combine whipping cream and 3 tablespoons sugar substitute, whisking until mixture simmers. Remove saucepan from heat and gradually whisk egg yolk mixture until thoroughly combined.
Distribute mixture evenly among 6 ramekins and place in 2 glass baking dishes. Pour hot water into baking dishes until it reaches halfway up sides of ramekins.
On middle rack, bake 30 minutes until set. After baking, sprinkle 1 tablespoon sugar substitute on each crème brûlée, then use culinary torch for 30 seconds to caramelize sugar. Refrigerate 10 minutes until set