Streusel:
1/2 CUP ALL-PURPOSE FLOUR
1/2 CUP (PACKED) LIGHT BROWN SUGAR
1/2 TEASPOON GROUND ALLSPICE
5 TABLESPOONS COLD UNSALTED BUTTER, CUT INTO BITS

Muffins:
2 CUPS ALL-PURPOSE FLOUR
1/2 CUP SUGAR
1 TABLESPOON BAKING POWDER
1/2 TEASPOON GROUND ALLSPICE
1/4 TEASPOON SALT
1/4 CUP (PACKED) LIGHT BROWN SUGAR
1 STICK (8 TABLESPOONS) UNSALTED BUTTER, MELTED AND COOLED
2 LARGE EGGS
3/4 CUP WHOLE MILK
1/4 TEASPOON PURE VANILLA EXTRACT
GRATED ZEST OF 1 LEMON (OPTIONAL)