Preheat oven to 425 degrees F. Melt butter and add oil to a large frying pan over medium-high heat. Add onions or leeks, thyme sprigs and a good shake of salt. Cook, stirring frequently for about 5 minutes, until the onions or leeks soften. Add garlic and turn heat down to medium, and allow onions or leeks to continue to cook until they develop some color, about 5 more minutes.

Add artichoke hearts, asparagus, and fresh peas, if using. Cook, stirring frequently for another 3 – 4 minutes. Add frozen peas now, if using. Pick out thyme sprigs, leaving as many leaves as possible.

Line a baking sheet with parchment or foil, shiny side up. Place pie crust on a floured work surface and roll it into a 12-inch round. Place goat or cow’s milk cheese in a small bowl. Using a fork blend vanilla powder or extract into the cheese. If the cheese is dry, add a little heavy cream and blend well. Sprinkle half the cheese over the bottom of the pastry crust, leaving a 2-1/2-inch border on all sides. Add the vegetable mixture, then crumble remaining cheese over the top of the vegetables.

Carefully transfer the galette to a pizza pan or baking sheet and bake for 20 – 25 minutes, or until pastry is lightly browned. Cut heat to 375 and bake until crust is browned and all vegetables are tender. Move to a cooling rack and allow the galette to rest for 15 – 20 minutes before cutting and serving.