Dissolve yeast and sugar in warm water; let set for 3-4 minutes, until bubbly.
Pour into bowl of stand mixer fitted with a bread hook.
Pour in one cup of flour, salt and sour cream. Mix on low for 30 seconds.
Turn mixer off; add second cup of flour. Turn mixer back on low and mix together until dough starts to come together.
Gradually add remaining cup of flour until the mixture forms a ball that pulls away from sides of the bowl. Once dough comes together, mix for another minute; then turn off mixer. Cover dough. Let rise for 1-2 hours.
Turn dough onto floured surface and divide into 2 pieces. Place on a baking sheet lined with parchment paper. Cover and let set for another 20 minutes.
Stir corn starch and water together in a microwave-safe bowl. Microwave on high for 30-40 seconds until mixture starts to bubble. Remove and let set.
Preheat oven to 375. Uncover dough and gently coat with corn starch mixture. Use a knife to cut a crisscross pattern on top. Bake for 25-30 minutes.
Remove from oven and let cool slightly. Use a serrated knife to cut a hole around the top. Hollow out inside of bread bowl (I used a fork). Time for soup!