Pat the chicken dry with paper towels and cut it into even 1-inch pieces.
Season the chicken with paprika, salt, and black pepper, tossing until the pieces are evenly coated.
Heat the olive oil in a large skillet over medium-high heat. Add the chicken in a single layer, working in two batches if necessary.
Cook for 3 to 4 minutes without moving the chicken, then turn the pieces and cook for another 3 to 4 minutes, or until golden and the thickest pieces reach 165°F (74°C).
Reduce the heat to medium-low. Add the butter and minced garlic and cook for 30 to 60 seconds, stirring, until the garlic is fragrant but not browned.
Return any cooked chicken batches to the skillet and toss everything in the garlic butter. Stir in the lemon juice, if using.
Remove from the heat, sprinkle with chopped parsley, and serve warm.