Make the dough: Heat the water to 100 degrees F in a bowl in the microwave. (It should feel warm but not too hot.) Sprinkle the yeast and 1/4 teaspoon granulated sugar over the top and stir to dissolve. Let stand until foamy, about 5 minutes.
Meanwhile, whisk the flour, milk powder, fine salt and the remaining 2 tablespoons granulated sugar in a large bowl and make a well in the center. Whisk the melted butter and egg yolks into the yeast mixture, then pour into the well and stir with a wooden spoon until the dough comes together into a shaggy ball.
Turn the dough out onto a lightly floured surface, dust with more flour and knead, adding more flour as needed, until smooth but still slightly sticky, 2 to 3 minutes. Transfer the dough to a buttered bowl, turning to coat. Cover with plastic wrap and let rise in a warm place until doubled in size, 1 to 1 1/2 hours.
Make the filling: Mix the granulated sugar, brown sugar and cinnamon in a small bowl. Turn out the dough onto a lightly floured surface, pat and roll out into a 10-by-18-inch rectangle. Spread the butter over the dough, leaving a 1-inch border on one long side. Sprinkle with the cinnamon sugar and lightly press into the butter. Brush the clean edge with water, then tightly roll up the dough into a log, starting with a long side and rolling toward the clean edge; pinch the seam to seal.
Butter a 9-by-13-inch baking dish and lightly sprinkle with granulated sugar. Slice the dough log into 12 pieces and arrange cut-side up in the dish. Cover with plastic wrap and let sit at room temperature until doubled in size, about 1 hour, or you can refrigerate overnight, then in the morning let stand at room temperature 2 hours before baking.
Preheat the oven to 350 degrees F. Uncover the rolls and bake until golden brown, 25 to 30 minutes. Let cool at least 15 minutes in the baking dish.
Meanwhile, make the toffee-pecan sauce: Bring the butter, brown sugar, corn syrup, heavy cream and kosher salt to a boil in a saucepan. Reduce the heat to a simmer and cook until thickened, 8 to 12 minutes. Stir in the pecans. Cook, stirring, until coated, 1 to 2 minutes. Let cool 5 minutes, stirring occasionally, then pour over the rolls.