Measure 2 cups flour into the mixing or mixer bowl the bowl and add the salt and yeast. In a small saucepan stir together the butter, milk, sour cream, and egg yolk. Place over low heat to warm to the touch. Do not let simmer or it will cook the egg.

Pour the liquid into the flour and blend by hand or with the mixer flat beater for 2 minutes, to make a smooth batter. Add flour, 1/4 cup at a time. Mix vigorously with a wooden spoon or dough hook. The dough will be smooth and soft.

Transfer the dough to a floured work surface, if by hand, or leave in the bowl under bowl under hook. The dough should be soft but not sticky. If sticky, add sprinkles of flour. Knead for 8 to 10 minutes, until the dough is velvety and responsive under your hands.

Press the dough into a flat oval and spread with 1/2 cup cheese. Turn in the sides and knead. Again press the dough into an oval, and add 1/4 cup more cheese. Knead until the cheese is spread throughout the dough, about 4 minutes.

BY PROCESSOR

Attach the steel blade.

Heat the moist ingredients in a saucepan, as above. The butter need not be completely melted. Measure 2 cups flour into the work bowl and sprinkle in the salt and yeast. Pulse to blend.

With the processor running, slowly pour the liquid in a stream through the feed tube. Add flour, 1/4 cup at a time, through the feed tube until the dough becomes a ball riding on the blade and cleans the sides of the bowl.

KNEADING

Once the dough forms a ball, process for 45 seconds.

If the dough is dry and hard, add water by the tablespoon. If the dough is wet and sticks to the sides of the bowl, add flour by the tbsp and process for a few more seconds.

Turn the dough from the bowl, and knead for a few moments to be certain the dough has the proper consistency. Work in the cheese and knead, as above.

CHILL

Press the dough into a flat oval, wrap with plastic wrap or place in a plastic bag, and chill overnight in the refrigerator.

The following day leave the dough at room temperature for 1 hour, then roll into a flat piece about 1/4" thick. Fold and roll once or twice more to make it flaky.

Preheat the oven to 350°.

SHAPING

Cut the dough with a 1" cookie cutter; turn each piece over and place bottom up on the baking sheet (this permits maximum rise). Lightly score each scone twice across the top with a sharp knife, brush with the egg wash, and sprinkle with the balance of the cheese (1/4 cup).

BAKING 350°

Place the sheet on the middle shelf of the moderate oven and bake until the scones are a golden brown, about 30 minutes.

(If using a convection oven, reduce heat 50°. Plan to bake in since more batches since most home convection ovens will not accommodate large baking sheets.)

Remove from the sheet and place on a metal rack to cool-although they are delicious still warm from the oven.

They can be frozen for months.