Core the pears and slice them thinly (about 1/8" thick). Place slices in a bowl and toss with the lemon juice to prevent browning and to brighten flavor. Set aside.

Slice Brie

Trim the Brie into 1/4" slices that will fit on the bread slices. If the Brie is very soft, chill briefly (10 minutes) to make slicing easier.

Bread & assembly

Prep and toast bread

Preheat oven to 375°F (190°C). Lightly brush both sides of the bread slices with olive oil (or spread butter on one side). Arrange slices on a baking sheet in a single layer. Toast in the oven 6–8 minutes, flipping once, until golden and crisp at edges.

Butter (optional)

If using butter instead of olive oil, spread a thin layer on the warm toasted bread immediately after it comes out of the oven.

Assemble crostini

Place a slice of Brie on each warm toast while still warm (this helps the Brie soften). Top each with 2–3 pear slices arranged nicely.

Garnish & finishing

Add honey & nuts

Drizzle about 1/2 tsp honey over each assembled toast (reserve remaining honey). Scatter chopped toasted walnuts over the toasts.

Season & serve

Sprinkle each toast with a few thyme leaves, a light pinch of flaky sea salt, and a grind of black pepper. If desired, warm the assembled toasts in the oven 2–3 minutes to just melt the Brie slightly and meld flavors. Transfer to a serving plate and finish with the remaining honey drizzled lightly over all crostini. Serve immediately.