Preparation

• In a large bowl, stir together 3 ounces flour, the milk, 1 tablespoon sugar, ¼ teaspoon yeast, and 1 egg with a fork until combined. Let rest 1 hour, then refrigerate overnight.
• Transfer the batter into the bowl of a stand mixer fitted with the dough hook attachment. Set aside.
• In a large bowl, whisk together the remaining 6 ounces flour, 2 tablespoons sugar, 1¼ teaspoons yeast and the salt until combined. Pour over the top of the existing dough and let rest 2 to 3 hours, until the dry mix starts to look cracked on top.
• Add 2 cold eggs and mix on medium speed until combined, 2 minutes. With the mixer running, add 8 tablespoons butter 1 tablespoon at a time, letting the dough absorb each addition before adding the next tablespoon. When the mixture is combined and the dough is smooth, about 2 minutes, scrape it into a large well-oiled mixing bowl.
• Let rise 2 hours, then cover with plastic wrap, pressing down to push the wrap gently into the dough. Refrigerate the dough at least 2 hours or overnight.
• Line a baking sheet with a silicone mat or parchment paper. Divide the dough into 8 to 10 equal pieces and place them 1 to 2 inches apart. Use your hands to gently flatten the dough, then let rise 1½ hours.
• Preheat the oven to 375 degrees.
• In a small bowl, beat 1 egg. Brush the rolls with the egg wash and sprinkle with the pearl sugar. Bake 10 to 12 minutes, until golden. Let cool completely.
• Meanwhile, in the bowl of a stand mixer, beat together the chocolate hazelnut spread, heavy cream and the remaining 2½ tablespoons butter on high speed until fluffy, adding more cream as needed if the mixture is too stiff.
• Slice the rolls in half and evenly divide the filling among the bottom halves, then top with a few strawberry slices. Replace the top halves and serve.