Toast the walnuts in a dry 20 cm / 8-inch skillet over medium heat for 3 to 4 minutes, stirring often, until fragrant and lightly browned. Let cool, then roughly chop.
Trim the base of each endive head and separate the leaves. Rinse and pat completely dry with a towel. Keep the sturdy, cup-shaped outer leaves for boats and save the small inner ones for a salad.
Core the pear and slice it thinly. Toss the slices with the lemon juice in a small bowl right away to stop browning.
Arrange the endive leaves cut side up on a serving platter.
Tuck one or two pear slices into each leaf.
Crumble the blue cheese evenly over the pear slices.
Scatter the toasted walnuts over the top of each boat.
Drizzle honey over the boats, then sprinkle with fresh thyme leaves, a crack of black pepper and a pinch of flaky salt if using.
Serve right away while the endive is still crisp.