Hazelnut Cardamom Sourdough Babka

DOUGH: 275g All Purpose Flour ( 2 Cups ) 200g Fed Sourdough Starter ( 3/4 Cup Stirred Down ) 125g Milk ( 1/2 Cup ) 75g Plain Yogurt ( 1/4 Cup ) 5g Kosher Salt ( 1Tsp ) Splash of Milk Prior to Baking FILLING: 71g Salter Butter Softened ( 5 Tbsp. ) 56g Sugar…