1. Preheat oven to 400 degrees and line a large baking sheet with foil. Lay bacon in a single layer onto baking sheet. Bake until crispy, about 15 to 25 minutes. Remove from oven and put slices on a plate with paper towel. Let cool. Once cool, crumble or cut bacon into 1 inch pieces. Reduce heat on oven to 375 degrees.
2. Heat a pan over medium heat and melt butter. Add leeks and cook until softened, about 3-5 minutes. Remove from heat and let cool.
3. In a large bowl, whisk eggs together. Add cream, milk, cheese, and salt and pepper and mix well. Fold in bacon and leeks.
4. Place 6 tart shells on a baking sheet. Portion out quiche mixture evenly between tart shells and bake for about 25 to 30 minutes, or until quiche is set. Remove from oven and serve with a side salad.