My Mom's Extraordinary Chocolate Chip Cake

• 15 secon the butter
• 6 p
• 1 egg
• 3/4 baking (pan)
• 450 gr packed brown sugar (lightly)
• 350 gr semisweet chocolate chips
• 250 gr all purpose flour
• 240 ml sour cream
• 65 gr butter (cold unsalted)
• 30 ml milk