1Heat oven to 350°F. Mix all the dry ingredients together. Cut in softened butter. Gently fold in the sour cream and vanilla. Fold in blueberries. Do not overwork the dough.
2Scoop dough (about 1/3 cup) onto two lightly greased baking sheets. Bake 30 minutes or until golden brown. Cool 5 minutes.
3Zest one lemon with a microplane grater. Cut all threee lemons in half; juice. In a medium sauce pan over medium heat, whisk together the lemon zest, lemon juice, eggs and sugar. Whisk constantly; do NOT boil. Once the mixture is hot, turn the heat to low and whisk in the butter, 1 tablespoon at a time. Continue cooking on low for 6 minutes until the lemon glaze has thickened. Remove from heat and let cool.
4Serve warm scones with lemon glaze. Store any leftover lemon glaze in refrigerator.