1. Spread pecans in a 10-inch tart pan with removable rim and bake in a 350° oven until golden in the center (break one to check), 8 to 12 minutes. Let cool.
2. In a food processor, whirl nuts, flour, brown sugar, and butter until fine crumbs form. Add vanilla and egg yolk; whirl until mixture comes together in a ball.
3. Press dough evenly over bottom and up sides of tart pan. Bake in a 350° oven until deep golden, 15 to 20 minutes. Let cool.
4. In a bowl, with an electric mixer on medium speed, beat cream cheese, sour cream, and powdered sugar until smooth. In another bowl, mix peaches with lemon juice.
5. Spread cream cheese mixture over bottom of pastry. Sprinkle mint on top, if using. Overlap peach slices in circles over cheese. Scatter blueberries over peaches.
6. Put jam in a 1-cup glass measure and cook, uncovered, in a microwave oven at full power (100%) until melted, 30 to 45 seconds. Brush over fruit.
7. Serve, or chill uncovered up to 1 hour. Remove pan rim and cut tart into wedges.
Wine: An earthy-floral dessert wine such as a late-harvest Gewürztraminer.