Mix flour, sugar, baking soda, baking powder, poppy seeds, lemon zest, and salt in a medium bowl.
Grate chilled butter on a cheese grater and incorporate into the dry mixture. Form a crater in the dry ingredients, and add the buttermilk, and vanilla extract. Mix until it comes together and dump onto a floured surface.
Knead dough slightly until it comes together. With your fingers, press out the dough into a rectangle about 10×6 inches. Cut into 8 rectangles.
Place shortbread on a cookie sheet and bake in preheated oven for about 14-16 minutes.
Mix glaze ingredients together and pour over the cooling biscuits.
Place defrosted strawberries in a medium bowl with sugar and lemon juice, and let macerate for 10 minutes.