Melt butter, stir in maple syrup and salt. Simmer 20 sec, brush/dab on bread, spread on foil + paper lined tray.
Lay prosciutto on the second tray (slight overlap is fine). Put both trays in 180C/350F (160C fan) oven.
At 15 min - remove prosciutto (should be dark red and wrinkled). Cool on paper towels until crisp, then break into shards.
At 15 min - flip crostini. Bake 5 more min until lightly crisp but not fully hard. Cool 10 min+ (crisps more).
Top crostini with brie, prosciutto shards, pecans, a drizzle of maple, and thyme leaves. Serve!
