Preheat the oven to 450°F and line a 12 cup muffin pan with paper liners.
In a large mixing bowl, combine the wet ingredients and mix well with a whisk until all the ingredients are well combined.
In a separate bowl, combine the dry ingredients and mix well with a flat whisk until evenly combined; set aside.
Add the grated cheese and chopped walnuts to the dry ingredients and mix well, then throw this mixture in with the wet ingredients; mix delicately with a large wooden spoon or rubber spatula until just incorporated, no more.
Divide the batter equally between the muffin cups; the batter will mound higher than the paper cups, that's perfectly normal. If you preferred smaller muffins, you could also divide the batter between 18 to 24 paper cups, instead. Of course, you'd need to adjust cooking time accordingly.
Place the pan in the 450°F oven for 10 minutes and then lower the oven temperature to 350°F. Continue baking for another 18-20 minutes, or until the tops are nice and golden brown and a toothpick inserted in the center of a muffin comes out clean.
Let the muffins cool for a few seconds in the pan and then remove them to a cooling rack to cool completely.
Store in the refrigerator in an airtight container for up to a week.