Chocolate Chocolate Chip Sheet Cake

Ingredients

• 2-1/2 cups all-purpose flour
• 1 (3.9 ounce) package chocolate instant pudding mix
• 1/2 cup unsweetened cocoa powder
• 2 teaspoons baking soda
• 1 teaspoon kosher salt
• 2 cups granulated sugar
• 1 cup canola oil
• 1 cup whole milk
• 1 large egg
• 1 teaspoon vanilla
• 1 cup water
• 1 cup mini chocolate chips
• 1 cup semi-sweet chocolate chips, melted and slightly cooled
• 1 cup (2 sticks) unsalted butter, softened
• 4 cups powdered sugar
• 3-4 tablespoons milk
• 1 cup mini chocolate chips, for garnishing