Grate enough lemon to yield 3 tablespoons of zest. Squeeze the lemons to yield ½ cup lemon juice. In a saucepan, bring milk and heavy cream to a simmer, stirring often. Add lemon zest, stir and set aside to steep for 15 minutes. In a bowl combine ¾ cup sugar, flour, baking powder and salt, whisking to combine. Add lemon juice, 2 egg yolks and vanilla, whisking to combine. Strain the lemon zest from milk mixture and pour milk mixture into bowl, stirring to combine. In a separate bowl, beat 4 egg whites until frothy, about 2 minutes. Add ¼ cup sugar and continue beating until stiff peaks are formed. Add 1/3 of the egg whites and whisk into egg mixture. Gently fold in remainder of egg whites until smooth and creamy. Line a large casserole dish or roasting pan with a kitchen towel. Place 6 (4-6oz) ramekins in pan. (The towel is so the ramekins don’t rattle during baking process.) Fill the pan with water enough to go up 1/3 of the ramekin. Bake at 350 degrees for about 50 minutes. Remove from oven and let ramekins set in the water for 10 minutes. Remove and serve with a dollop of whipped cream or cool whip on top. Delicious room temperature or chilled.