Preheat oven to 375°. Line 2 baking sheets with parchment paper.
In a large bowl, whisk together all-purpose flour, buckwheat flour, and ¼ teaspoon salt. Using a pastry blender or 2 forks, cut in cold butter until it resembles fine crumbs. Add cream, stirring until dough comes together.
Turn out dough onto a lightly floured surface, and gently knead for approx-imately 1 minute. Shape dough into a disk, and wrap in plastic wrap. Let stand at room temperature for 30 minutes.
Turn out dough onto a lightly floured surface. Using a rolling pin, roll dough into a 16x8-inch rectangle. (Dough should be very thin.) Using a fork, poke holes evenly across surface of dough. Using a sharp knife, cut dough into 30 (2½x1½-inch) rectangles. Place rectangles on prepared baking sheets. Brush tops of rectangles with oil, and sprinkle with remaining ¾ teaspoon salt.
Bake until crackers are crisp, 10 to 12 minutes. Transfer to a wire rack, and let cool completely.
Notes
Make-Ahead Tip: Crackers can be made up to 2 days in advance and stored in an airtight container at room temperature.
Recipe by TeaTime Magazine at https://teatimemagazine.com/herbed-mushroom-buckwheat-canapes-recipe/