Preheat the oven to 375°F (190°C). Lightly oil a 9-inch (23 cm) tart pan or pie dish with olive oil or vegan butter.

To make the crust, combine the all-purpose flour, whole-wheat flour, sugar, and salt in a large mixing bowl. Add the cold, diced vegan butter. Use a pastry cutter or fork to cut the butter into the flour until the mixture resembles coarse crumbs.

Gradually add the cold water, stirring just until the dough holds together.

Turn the dough onto a lightly floured surface and knead briefly just until smooth. Flatten into a disc, wrap, and toss it in your freezer for 15 minutes.

On a floured surface, roll out the chilled dough to fit the tart pan. Press it into the pan and trim any excess from the edges. Prick the base several times with a fork. Line the crust with parchment paper and fill with pie weights or dried beans. Bake for 15 minutes, then remove the parchment and weights. Remove from the oven and set aside.

While the crust bakes, prepare the filling. In a mixing bowl, combine the just egg, vegan cream cheese, vegan cheddar, plant-based milk, and minced garlic. Whisk until smooth. Fold in the broccoli, chives, thyme, sage, parsley, and black pepper.

Pour the filling into the partially pre-baked crust and smooth the surface. Bake at 375°F (190°C) for 35-40 minutes, or until the center is set and the top is lightly golden.

Let the quiche rest for 10-12 minutes before slicing so that it firms up and cools a little. Garnish with additional chives or fresh herbs if desired. Serve warm or at room temperature.