Make the pastry:

1. Whisk the flour, salt and pepper together in a large bowl. Place a box grater over the bowl and grate the butter on the large holes.
2. Gently toss the gated butter in the flour to distribute it evenly.
3. Stir in the ice water with a fork until the flour is evenly moistened (If the dough seems dry, add 1 to 2 teaspoons of water and stir until combined)
4. Scrape the dough onto a work surface and knead gently until the dough comes together (about 2 minutes) Shape it into a disk, wrap it in plastic and refrigerate for an hour.
5. While the dough is in the fridge, place the potatoes, zucchini, mushrooms asparagus, red onion and red peppers in a large bowl. Add the salt, pepper, thyme leaves and olive oil. Set aside.
6. Preheat the oven at 450F.
7. In a small bowl, stir the sour cream and parmesan cheese.
8. Take the dough out of the fridge, and spread the cream mixture evenly over the dough, leaving a 1 1/2 -inch uncover edge all around.
9. Scatter the vegetable mixture on the cream mixture. Fold the edge pf the pastry up and over the vegetables, to create a folded-over border and an exposed center. Top with the mini vine tomatoes.
10. Lightly brush the edge of the dough with milk, being careful not to let any milk drip beneath the dough.
11. Bake the galette for 25 minutes, until the pastry is lightly browned and the vegetables are tender. Let the galette Cool slightly on the baking sheet. Serve warm or at room temperature. Enjoy!