• First, preheat the oven to 350˚ F, and line 11 cups in a standard-size muffin pan with liners.

Starting with the muffins

• In a large bowl, whisk together the melted butter, egg yolk, buttermilk, and vanilla.
• Next, sprinkle the flour, baking powder, baking soda, salt, brown sugar, cinnamon, and cloves on top of the butter mixture.
• Stir very well to combine everything. The batter will seem slightly dry, and that's fine--make sure all the flour is incorporated.
• Stir in the chopped pears.
• Divide the batter between the muffin cups.

To make the streusel

• In a small bowl, stir together the melted butter, flour, oats, and sugar. The streusel will clump together into a wet mixture.
• Use your fingers to pinch off small pieces of it to crumble over the muffin tops, about a scant teaspoon per muffin.
• If desired, fan 3 thin slices of pear on top of each muffin.
• Bake the muffins for 23-25 minutes.
• Immediately remove the muffins from the pan when they're done and let cool on a wire rack for 10 minutes before serving.
• Leftover muffins keep for 1 day on the counter, tightly covered.