In a large bowl, combine the flour and yeast. Gradually add the water and mix until a rough dough forms. Knead 5 to 7 minutes until smooth and slightly sticky, wetting your hands as needed. Add the salt and oil and knead briefly to incorporate. Cover with plastic wrap and a towel, and let rise at room temperature for 1 hour, or refrigerate for at least 8 hours and up to 72 hours.
Turn the dough out onto a lightly floured surface and divide into four pieces, about 7.4 ounces/210 grams each. Shape into balls, coat lightly with flour, and cover until ready to use. If chilled, bring to room temperature before shaping.
Preheat the oven to 450°F/230°C and position a rack in the middle. If using an inverted baking sheet as a stone, place it in the oven to heat.
Whisk together the sour cream, honey, cornstarch, sugar, and cream cheese until smooth. Roll one dough ball into an oval about 7x5 inches/18x13 centimeters on a surface dusted with semolina or cornmeal.
Spoon 3 tablespoons of filling down the center, leaving a 1-inch/2.5-centimeter border. Scatter a quarter of the white chocolate over the filling. Fold the dough over and press the edges firmly to seal.
Transfer seam-side down to parchment on an inverted baking sheet or hot stone. Repeat with remaining dough and filling.
Bake until golden and puffed, about 10 minutes. Let rest briefly, then serve warm.