Preheat the oven to 350°F (180°C). Line a baking sheet with parchment paper.
Melt the butter in a medium pan over medium heat. Add the onion and salt and cook until the onion is golden brown, about 10 minutes. Add the thyme and cook for another 2 minutes, until fragrant.
Slice the croissants in half horizontally and place on the prepared baking sheet, cut-side up. Spread the apricot preserves over the top halves of the croissants, then layer on 3 slices of Brie. Divide the caramelized onions between the bottom croissant halves, then top with the Castle Wood Reserve® Uncured Honey Ham.
Bake the open-face croissants for 10 minutes, until the cheese is melted.
Remove the croissants from the oven and add the arugula. Close the sandwiches and serve each with a skewered strawberry for garnish.