Below I've shared the recipe I use, but I'm also tempted by this one and this lighter version too--both recent discoveries.
1 3/4 lbs. carrots, peeled and chopped
1 cup sugar
1 1/2 tsp. baking powder
1 1/2 tsp. pure vanilla
2 tB. all purpose flour
3 eggs, beaten
1/2 cup butter
confectioners sugar for dusting
Preheat oven to 350 degrees F (175 degrees C). In a large pot of boiling water, cook the carrots until very tender. Drain, and transfer to a large mixing bowl. While the carrots are warm, use an electric mixer to beat with sugar, baking powder and vanilla extract until smooth. Mix in the flour, eggs, and butter. Transfer to a 2 quart baking dish. Bake one hour in the preheated oven, or until top is golden brown. Dust lightly with confectioners' sugar before serving.
Note: If you want to use individual ramekins instead of one dish, adjust the cooking time to about 30-35 minutes depending on your oven. Keep an eye on them to avoid over-cooking them. I read online that one person liked to puree the carrots with the butter, sugar and vanilla and then add in the baking powder with the eggs and flour. Apparently the souffle rises better. I think I'll try that next time.