Heat a charcoal or gas grill to medium-high.
Whisk the green peppercorns into the vinaigrette. Set aside.
Brush the asparagus with olive oil and season with salt and pepper. Grill until golden brown on all sides and crisp-tender, 4 to 5 minutes total. Remove from the grill, cut into 1- to 2-inch pieces, and toss with some of the vinaigrette.
Brush the bread on one side with canola oil and season with salt and pepper. Grill, oiled-side down, until light golden brown and crisp, about 1 minute. Flip, and grill a few seconds more, just enough to warm¿the bread should still be tender when pressed.
Top the toasted bread with some asparagus. Scatter the goat cheese, if using, on top and serve immediately.
In a medium bowl, whisk together the lemon juice, zest, mustard, tarragon, honey, and a little salt and pepper. Gradually whisk in the olive oil until emulsified.