Pat chicken thighs completely dry with paper towels. This is crucial for browning. Season both sides with salt and pepper. Let sit at room temperature while you prep the sauce ingredients.

In a small saucepan, combine 1.5 cups blueberries, minced jalapeno, shallot, chicken broth, balsamic vinegar, honey, and thyme. Bring to a boil over medium-high heat, then reduce to a simmer. Cook 10-12 minutes, stirring occasionally, until berries burst and sauce thickens enough to coat the back of a spoon. Remove from heat and keep warm.

Heat olive oil and 0.5 tbsp butter in a large oven-safe skillet over medium-high heat until shimmering. Add chicken thighs in a single layer, working in batches if needed. Cook undisturbed 5-6 minutes until deeply golden brown. Flip and cook 3-4 minutes more. Chicken should register 165F in the thickest part. Transfer to a plate and tent with foil.

Pour the blueberry mixture into the same skillet, scraping up any browned bits. Add remaining 0.5 tbsp butter and swirl until melted. Stir in remaining 0.5 cup fresh blueberries and cook 2 minutes just until they soften slightly but still hold their shape. Taste and adjust - add more honey if too spicy, more vinegar if too sweet.

Return chicken and any accumulated juices to the skillet, turning to coat in sauce. Serve directly from the pan or transfer to a platter. Spoon extra sauce over top and garnish with jalapeno slices and thyme sprigs. Serve with rice, polenta, or crusty bread to soak up every drop.