For the Filling:

1. Place the sliced pears in a bowl and toss with the lemon juice. In another large bowl, stir together the powdered sugar and the flour. Add the sliced pears and toss to coat.
2. In a separate bowl, stir together the yogurt, egg, cream, vanilla, and a dash of cinnamon. Add this to the pear mixture, and stir until evenly coated. Pour the whole mixture into the unbaked pie shell.

For the Streusel Topping:

1. Mix together the flour and the sugar in a small bowl. Cut in the butter with a fork or pastry cutter until the mixture is crumbly.
2. Sprinkle evenly over the top of the pie.

For Baking and Serving:

1. Bake for 10 minutes at 400°F, then reduce the temperature to 350°F. Bake for an additional 45-50 minutes, or until pears are tender and the streusel topping is golden brown.
2. Remove from the oven and let cool on a cooling rack for 15 minutes. Let chill completely in the refrigerator for 8 hours, or overnight.
3. Serve chilled or warmed. Enjoy!