Make dough. In a bowl of your stand mixer with a paddle attachment, stir together the flour (start with 4 cups), yeast, sugar and salt. Add in the eggs, vanilla and milk and stir to combine. Then add in the softened butter a few pieces at a time and stir to combine until a shaggy dough comes together. Dough will be very sticky and shaggy at this point - do not add more flour at this point. 4 ½ cups (540 g) all purpose flour ½ cup (100 g) granulated sugar 2 ¼ teaspoons instant yeast 1 teaspoon fine sea salt 2 large eggs 2 teaspoons vanilla extract 6 tablespoons (85 g) unsalted butter,
Knead the dough. Fit the mixer with a dough hook attachment, and knead at medium speed for 6-8 minutes. If the dough is super sticky, add additional flour a little at a time if needed. If you are kneading the dough by hand, then turn the dough out onto a lightly floured surface and knead for 8-10 minutes by hand. Dough will be sticky at first, and get less sticky as you knead, so I add extra flour a tablespoon at a time if needed. The dough should still be slightly sticky to the touch but feel smooth and elastic. Do not use more than 5 cups of flour and not over knead or your cinnamon rolls will become out dense and chewy!
Let the dough rise. Lightly grease a large bowl, and place dough into the bowl, turning once to coat. Cover the bowl and allow to rise until doubled in size, about 1 to 1 1/2 hours. If you're using active dry yeast, the rise time will take longer.
Roll out the dough. Turn the dough out onto a lightly floured surface, and roll out the dough into a 18x12 inches rectangle.
Spread filling. Spread the jam over the dough into an even layer, leaving about a ½-inch border at the top long edge. Sprinkle on the diced strawberries. ½ cup strawberry jam 1 cup fresh strawberries
Cut rolls. Starting on the long edge with filling, roll up the dough tightly into a log. Pinch the dough to seal. Using a serrated knife cut the log into 12 equal rolls. You can also cut the rolls using a piece of thread or unflavored dental floss,which I find gives the cleanest cuts. I place a long piece of thread underneath the dough, bring up the thread on each side, criss cross it, and then pull the thread through the dough so it cuts right through leaving the spiral intact.
Let rolls rise. Grease a 9”x13” baking dish with butter or non-stick cooking spray. Place rolls into pan spiral side up. Cover the baking dish and let rise in a warm, draft free place for 45 minutes until the rolls are slightly puffy, and nearly doubled in size. If you used active dry yeast, the second rise time will be near 75 minutes.
Bake rolls. Near the end of the second rise time, position a rack in the center of your oven and preheat the oven to 350°F/177°C. Bake rolls in the preheated oven for 30-35 minutes until golden brown. Let cool in the pan for about 20 minutes before icing.