Preheat the oven to 350 F. Line the bottom and sides of an 8 ½ by 4 ½ inch loaf pan or 2 small ceramic pans with parchment paper.
Beat the butter, sugar, and eggs with the paddle attachment of a stand mixer on medium for about 2 minutes or use a handheld mixer and beat for beat for 3-4 minutes.
Add the rice and buckwheat flours, baking soda, baking powder, cinnamon, nutmeg, salt, pumpkin puree and beat on low speed until smooth.
If using chocolate chips, fold them in as well.
Scrape the mixture into the prepared pan (or pans). If using small loaf pans, set them ona rimmed baking sheet.
Bake for for 45 -50 minutes, or until a toothpick inserted into the center comes out clean. If making 2 small (3x5 inch) loaves, the bread will most likely take at least 45 minutes. If you are making even smaller loaves, check at 35 minutes.